WO2017099052A1

WO2017099052A1 - Lubricant oil composition for internal combustion engine

Info

Publication number: WO2017099052A1
Application number: PCT/JP2016/086160
Authority: WO
Inventors: 耕治星野; 裕充松田; 豊治金子; 山守　一雄
Original assignee: Ｊｘエネルギー株式会社; トヨタ自動車株式会社
Priority date: 2015-12-07
Filing date: 2016-12-06
Publication date: 2017-06-15
Also published as: CN108473905B; DE112016005592B4; US20180334636A1; JP6895387B2; CN108473905A; DE112016005592T5; DE112016005592B9; JPWO2017099052A1

Abstract

According to the present invention, a lubricant oil composition for an internal combustion engine contains (A) a base oil having a kinematic viscosity of 2-8 mm²/s at 100°C and 10 mass% or less aromatic content, (B) a metal-based detergent including (B1) a metal-based detergent overbased by calcium carbonate and (B2) a metal-based detergent overbased by magnesium carbonate, and (C) molybdenum dithiocarbamate sulfide or oxymolybdenum dithiocarbamate sulfide; wherein, based on the total amount of the lubricant oil composition, the calcium content is 1500 or less ppm by mass, the magnesium content is 300 or more ppm by mass and the molybdenum content is 600 or more ppm by mass; and wherein the HTHS viscosity at 150°C is 2.7 or less mPa · s.

Description

Lubricating oil composition for internal combustion engines

The present invention relates to a lubricating oil composition for an internal combustion engine.

In recent years, it has been proposed to replace the conventional naturally aspirated engine with a lower-displacement engine (supercharged downsizing engine) equipped with a supercharger in order to reduce the fuel consumption of an internal combustion engine for automobiles, particularly an automobile gasoline engine. ing. According to the supercharged downsizing engine, by providing the supercharger, it is possible to reduce the exhaust amount while maintaining the output and to save fuel.

On the other hand, in a supercharged downsizing engine, if the torque is increased in the low speed range, a phenomenon (LSPI: Low Speed Pre-Ignition) may occur where ignition occurs in the cylinder earlier than the scheduled timing. is there. When LSPI occurs, energy loss increases and becomes a constraint on fuel efficiency improvement and low-speed torque improvement. The influence of engine oil is suspected in the generation of LSPI, and it has been reported that the Ca content in engine oil promotes the generation of LSPI.

International Publication No. 2015/114920 Pamphlet Japanese Patent Laid-Open No. 7-316577 JP 2014-152301 A JP 2015-143304 A JP 2015-140354 A Japanese Patent No. 5727701 International Publication No. 2015/111746

However, the Ca content in the engine oil is derived from a metallic detergent that is an additive for keeping the engine clean. Therefore, if Ca content is reduced to suppress LSPI, engine cleanliness will be insufficient this time.

An object of the present invention is to provide a lubricating oil composition for an internal combustion engine that has enhanced LSPI suppression capability and has both engine cleanliness and fuel efficiency.

In a first aspect of the present invention, (A) a base oil having a kinematic viscosity at 100 ° C. of 2 to 8 mm ² / s and an aromatic content of 10% by mass or less, and (B) (B1) carbonic acid A metal detergent comprising a metal detergent overbased with calcium and (B2) a metal detergent overbased with magnesium carbonate; and (C) molybdenum sulfide dithiocarbamate or sulfurized oxymolybdenum dithiocarbamate; , And based on the total amount of the lubricating oil composition, the calcium content is 1500 mass ppm or less, the magnesium content is 300 mass ppm or more, the molybdenum content is 600 mass ppm or more, and the HTHS viscosity at 150 ° C. Is a lubricating oil composition for an internal combustion engine, characterized in that it is 2.7 mPa · s or less.

In this specification, “kinematic viscosity at 100 ° C.” means the kinematic viscosity at 100 ° C. as defined in ASTM D-445. “HTHS viscosity at 150 ° C.” means the high temperature and high shear viscosity at 150 ° C. defined in ASTM D4683.

According to a second aspect of the present invention, there is provided an internal combustion engine comprising a step of operating the internal combustion engine while lubricating a cylinder of the internal combustion engine using the lubricating oil composition according to the first aspect of the present invention. This is a method of suppressing LSPI.

According to the first aspect of the present invention, it is possible to provide a lubricating oil composition for an internal combustion engine that has enhanced LSPI suppression capability and has both engine cleanliness and fuel efficiency.

Since the LSPI suppression method for an internal combustion engine according to the second aspect of the present invention uses the lubricating oil composition according to the first aspect of the present invention, it is possible to effectively suppress LSPI in the internal combustion engine.

It is the scatter diagram which plotted the occurrence frequency of LSPI in an engine test with respect to the DSC (10 atm) auto-ignition point of the engine oil sample used in the engine test.

Hereinafter, the present invention will be described in detail. Unless otherwise specified, the notation “A to B” for the numerical values A and B means “A to B”. In this notation, when a unit is attached to only the numerical value B, the unit is also applied to the numerical value A. Further, the terms “or” and “or” mean logical sums unless otherwise specified.

<(A) Lubricating base oil>
In the lubricating oil composition of the present invention, as a base oil, a lubricating base oil having a kinematic viscosity at 100 ° C. of 2 to 8 mm ² / s and an aromatic content of 10% by mass or less (hereinafter “present” The lubricant base oil according to the embodiment ”may be used.

As the lubricating base oil according to the present embodiment, for example, a lubricating oil fraction obtained by subjecting crude oil to atmospheric distillation and / or vacuum distillation is subjected to solvent removal, solvent extraction, hydrocracking, solvent dewaxing, Paraffinic mineral oil refined by one or a combination of two or more selected from purification processes such as catalytic dewaxing, hydrorefining, sulfuric acid washing, clay treatment, etc., normal paraffinic base oil, isoparaffinic base oil, and these Examples of the mixture include those having a kinematic viscosity at 100 ° C. of 2 to 8 mm ² / s and an aromatic content of 10% by mass or less.

As preferable examples of the lubricating base oil according to the present embodiment, the following base oils (1) to (8) are used as raw materials, and the raw oil and / or the lubricating oil fraction recovered from the raw oil is The base oil obtained by refine | purifying with a predetermined refinement | purification method and collect | recovering lubricating oil fractions can be mentioned.
(1) Distilled oil by atmospheric distillation of paraffinic crude oil and / or mixed base crude oil (2) Distilled oil by vacuum distillation of atmospheric distillation residue of paraffinic crude oil and / or mixed base crude oil ( WVGO)
(3) Wax (slack wax, etc.) obtained by the lubricant dewaxing process and / or synthetic wax (Fischer-Tropsch wax, GTL wax, etc.) obtained by the gas-to-liquid (GTL) process, etc.
(4) One or more mixed oils selected from base oils (1) to (3) and / or mild hydrocracked oils of the mixed oils (5) selected from base oils (1) to (4) 2 or more kinds of mixed oils (6) Base oil (1), (2), (3), (4) or (5) debris oil (DAO)
(7) Mild hydrocracking treatment oil (MHC) of base oil (6)
(8) Two or more mixed oils selected from base oils (1) to (7).

The above-mentioned predetermined purification methods include hydrorefining such as hydrocracking and hydrofinishing; solvent refining such as furfural solvent extraction; dewaxing such as solvent dewaxing and catalytic dewaxing; acid clay and activated clay White clay refining; chemical (acid or alkali) cleaning such as sulfuric acid cleaning and caustic soda cleaning are preferred. In the present invention, one of these purification methods may be performed alone, or two or more may be combined. Moreover, when combining 2 or more types of purification methods, the order in particular is not restrict | limited, It can select suitably.

Furthermore, the lubricating base oil according to the present embodiment is obtained by subjecting a base oil selected from the above base oils (1) to (8) or a lubricating oil fraction recovered from the base oil to a predetermined treatment. The following base oil (9) or (10) is particularly preferred.
(9) The base oil selected from the above base oils (1) to (8) or the lubricating oil fraction recovered from the base oil is hydrocracked and recovered from the product or the product by distillation or the like. Hydrocracking base oil (10) obtained by subjecting the lubricating oil fraction to dewaxing treatment such as solvent dewaxing or catalytic dewaxing, or distillation after the dewaxing treatment, and the above base oils (1) to ( The base oil selected from 8) or the lubricating oil fraction recovered from the base oil is hydroisomerized, and the product or the lubricating oil fraction recovered from the product by distillation or the like is subjected to solvent dewaxing or catalytic desorption. Hydroisomerized base oil obtained by performing dewaxing treatment such as wax or by distillation after the dewaxing treatment. As the dewaxing step, a base oil produced through a contact dewaxing step is preferable.

In addition, when obtaining the lubricating base oil of (9) or (10) above, a solvent refining treatment and / or a hydrofinishing treatment step may be further performed at an appropriate stage, if necessary.

The catalyst used for the hydrocracking / hydroisomerization is not particularly limited, but a composite oxide having cracking activity (for example, silica alumina, alumina boria, silica zirconia, etc.) or one kind of the composite oxide. Hydrogenolysis with a combination of the above combined with a binder and supporting a metal having hydrogenation ability (for example, one or more metals such as Group VIa metal or Group VIII metal in the periodic table) A hydroisomerization catalyst in which a catalyst or a support containing zeolite (eg, ZSM-5, zeolite beta, SAPO-11, etc.) is loaded with a metal having a hydrogenation ability containing at least one of the Group VIII metals Are preferably used. The hydrocracking catalyst and the hydroisomerization catalyst may be used in combination by stacking or mixing.

The reaction conditions in the hydrocracking and hydroisomerization are not particularly limited, but the hydrogen partial pressure is 0.1 to 20 MPa, the average reaction temperature is 150 to 450 ° C., the LHSV is 0.1 to 3.0 hr ⁻¹ , the hydrogen / oil ratio. 50 to 20000 scf / b is preferable.

The kinematic viscosity at 100 ° C. of the lubricating base oil according to this embodiment is 2.0 to 8.0 mm ² / s. Also, preferably not more than ^{5 mm} 2 / s, more preferably 4.5 mm ² / s or less, more preferably 4.4 mm ² / s or less, particularly preferably not more than 4.3 mm ² / s. On the other hand, the kinematic viscosity at 100 ° C. is preferably 3.0 mm ² / s or more, more preferably 3.5 mm ² / s or more, still more preferably 3.8 mm ² / s or more, particularly preferably 4. 0 mm ² / s or more. When the kinematic viscosity at 100 ° C. of the lubricating base oil exceeds 8.0 mm ² / s, the low-temperature viscosity characteristics of the lubricating oil composition may deteriorate, and sufficient fuel economy may not be obtained. If it is less than 0.0 mm ² / s, the formation of an oil film at the lubrication site is insufficient, resulting in poor lubricity, and the evaporation loss of the lubricating oil composition may be increased.

The kinematic viscosity at 40 ° C. of the lubricating base oil according to the present embodiment is preferably 40 mm ² / s or less, more preferably 30 mm ² / s or less, still more preferably 25 mm ² / s or less, particularly preferably 22 mm ² / s. Hereinafter, it is most preferably 20 mm ² / s or less. On the other hand, the kinematic viscosity at 40 ° C. is preferably 6.0 mm ² / s or more, more preferably 8.0 mm ² / s or more, further preferably 10 mm ² / s or more, particularly preferably 12 mm ² / s or more, most preferably Preferably it is 14 mm < ² > / s or more. When the kinematic viscosity at 40 ° C. of the lubricating base oil exceeds 40 mm ² / s, the low-temperature viscosity characteristics of the lubricating oil composition may be deteriorated, and sufficient fuel economy may not be obtained. If it is less than ² / s, the oil film formation at the lubrication site is insufficient, so that the lubricity is inferior, and the evaporation loss of the lubricating oil composition may increase.

In this specification, “kinematic viscosity at 40 ° C.” means the kinematic viscosity at 40 ° C. as defined in ASTM D-445.

The viscosity index of the lubricating base oil according to this embodiment is preferably 100 or more. More preferably, it is 110 or more, More preferably, it is 120 or more, Especially preferably, it is 125 or more, Most preferably, it is 130 or more. When the viscosity index is less than 100, not only the viscosity-temperature characteristics, thermal / oxidative stability and volatilization prevention properties of the lubricating oil composition deteriorate, but also the friction coefficient tends to increase, and the wear prevention property It tends to decrease. In the present specification, the viscosity index means a viscosity index measured according to JIS K 2283-1993.

The density (ρ ₁₅ ) at 15 ° C. of the lubricating base oil according to this embodiment is preferably 0.860 or less, more preferably 0.850 or less, still more preferably 0.840 or less, and particularly preferably 0.835 or less. It is. In this specification, the density at 15 ° C. means the density measured at 15 ° C. in accordance with JIS K 2249-1995.

The pour point of the lubricating base oil according to this embodiment is preferably −10 ° C. or lower, more preferably −12.5 ° C. or lower, still more preferably −15 ° C. or lower, particularly preferably −17.5 ° C. or lower, most preferably Preferably it is −20.0 ° C. or lower. When the pour point exceeds the above upper limit, the low temperature fluidity of the entire lubricating oil composition tends to be lowered. In this specification, the pour point means a pour point measured according to JIS K 2269-1987.

The sulfur content in the lubricating base oil according to this embodiment depends on the sulfur content of the raw material. For example, when a raw material that does not substantially contain sulfur such as a synthetic wax component obtained by a Fischer-Tropsch reaction or the like is used, a lubricating base oil that does not substantially contain sulfur can be obtained. In addition, when using raw materials containing sulfur such as slack wax obtained in the refining process of the lubricating base oil and microwax obtained in the refining process, the sulfur content in the obtained lubricating base oil is usually 100 mass ppm. That's it. In the lubricating base oil according to the present embodiment, the content of sulfur is preferably 100 ppm by mass or less, and 50 ppm by mass or less, from the viewpoint of further improvement in thermal and oxidation stability and low sulfur content. More preferably, it is more preferably 10 ppm by mass or less, and particularly preferably 5 ppm by mass or less.

The nitrogen content in the lubricating base oil according to this embodiment is preferably 10 ppm by mass or less, more preferably 5 ppm by mass or less, and even more preferably 3 ppm by mass or less. When the content of nitrogen exceeds 10 ppm by mass, the heat / oxidation stability tends to decrease. In the present specification, the nitrogen content means a nitrogen content measured in accordance with JIS K 2609-1990.

% C _P of the lubricating base oil according to the present embodiment is preferably 70 or more, more preferably 80 or more, more preferably 85 or more, and usually 99 or less, preferably 95 or less, more preferably 94 or less is there. When% C _P of lubricating base oil is less than the above lower limit value, viscosity-temperature characteristics, thermal / oxidative stability and friction characteristics tend to decrease, and when additives are added to lubricating base oil In addition, the effectiveness of the additive tends to decrease. Further, when the% C _p value of the lubricating base oil exceeds the upper limit value, the additive solubility will tend to be lower.

% C _A of the lubricating base oil according to the present embodiment is preferably 2 or less, more preferably 1 or less, more preferably 0.8 or less, particularly preferably 0.5 or less. When% C _A of the lubricating base oil exceeds the upper limit value, the viscosity - temperature characteristic, thermal and oxidation stability and fuel efficiency tends to decrease.

% C _N of the lubricating base oil according to the present embodiment is preferably 30 or less, more preferably 25 or less, more preferably 20 or less, particularly preferably 15 or less. The% C _N of the lubricating base oil is preferably 1 or more, more preferably 4 or more. If the% C _N value of the lubricating base oil exceeds the upper limit value, the viscosity - temperature characteristic, thermal and oxidation stability and frictional properties will tend to be reduced. Moreover, when% _CN is less than the said lower limit, it exists in the tendency for the solubility of an additive to fall.

In the present specification,% C _P ,% C _N and% C _A are the percentages of the number of paraffin carbons to the total number of carbons determined by a method (ndM ring analysis) based on ASTM D 3238-85, respectively. Mean the percentage of naphthene carbons to total carbons, and the percentage of aromatic carbons to total carbons. In other words, the preferred ranges of% C _P ,% C _N and% C _A described above are based on the values obtained by the above method. For example, even for a lubricating base oil containing no naphthene, it can be obtained by the above method. The% _{CN that} is obtained can exhibit values greater than zero.

The content of the saturated component in the lubricating base oil according to this embodiment is preferably 90% by mass or more, preferably 95% by mass or more, more preferably 99% by mass or more, based on the total amount of the lubricating oil base oil. is there. The proportion of the cyclic saturated component in the saturated component is preferably 40% by mass or less, preferably 35% by mass or less, preferably 30% by mass or less, and more preferably 25% by mass or less. More preferably, it is 21% by mass or less. Moreover, the ratio of the cyclic | annular saturated part which occupies for the said saturated part becomes like this. Preferably it is 5 mass% or more, More preferably, it is 10 mass% or more. When the content of the saturated component and the ratio of the cyclic saturated component in the saturated component satisfy the above conditions, the viscosity-temperature characteristics and thermal / oxidative stability can be improved. When the additive is blended, the function of the additive can be expressed at a higher level while the additive is sufficiently stably dissolved and held in the lubricating base oil. Furthermore, it is possible to improve the friction characteristics of the lubricating base oil itself, and as a result, it is possible to achieve an improvement in friction reduction effect and an improvement in energy saving. In the present specification, the saturated content means a value measured in accordance with ASTM D 2007-93.

In addition, a similar method that can obtain the same result can be used for the separation method of the saturated component or the composition analysis of the cyclic saturated component and the non-cyclic saturated component. For example, in addition to the method described in ASTM D 2007-93, the method described in ASTM D 2425-93, the method described in ASTM D 2549-91, the method by high performance liquid chromatography (HPLC), or these methods may be used. The improved method etc. can be mentioned.

The aromatic content in the lubricating base oil according to this embodiment is 10% by mass or less, preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3%, based on the total amount of the lubricating base oil. % By mass or less, particularly preferably 2% by mass or less, preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1% by mass or more, particularly preferably 1.5% by mass. % Or more. If the aromatic content exceeds the above upper limit, the viscosity-temperature characteristics, thermal / oxidative stability, friction characteristics, volatilization prevention characteristics and low-temperature viscosity characteristics tend to decrease. When an additive is blended with the additive, the effectiveness of the additive tends to decrease. Further, the lubricating base oil according to the present embodiment may not contain an aromatic component, but the solubility of the additive is further increased by setting the aromatic content to be equal to or higher than the above lower limit value. be able to.

In the present application, the aromatic content means a value measured according to ASTM D 2007-93. The aromatic component usually includes alkylbenzene, alkylnaphthalene, anthracene, phenanthrene and alkylated products thereof, and compounds having four or more condensed benzene rings, pyridines, quinolines, phenols, naphthols, etc. An aromatic compound having a hetero atom is included.

A synthetic base oil may be used as the lubricating base oil according to the present embodiment. Synthetic base oils include poly α-olefins and their hydrides, isobutene oligomers, having a kinematic viscosity at 100 ° C. of 2.0 to 8.0 mm ² / s and an aromatic content of 10% by mass or less. Its hydride, isoparaffin, alkylbenzene, alkylnaphthalene, diester (ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc.), polyol ester (trimethylolpropane caprylate) Trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, etc.), polyoxyalkylene glycol, dialkyldiphenyl ether, polyphenyl ether, And a mixture thereof. Among them, poly α-olefin is preferable. The poly α-olefin is typically an α-olefin oligomer or co-oligomer having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms (1-octene oligomer, decene oligomer, ethylene-propylene co-oligomer, etc.). And their hydrogenation products.

The production method of the poly-α-olefin is not particularly limited. For example, polymerization such as a catalyst containing a complex of aluminum trichloride or boron trifluoride with water, alcohol (ethanol, propanol, butanol, etc.), carboxylic acid or ester. A method of polymerizing α-olefin in the presence of a catalyst can be mentioned.

The lubricating base oil according to the present embodiment has a single base oil as long as the base oil as a whole has a kinematic viscosity at 100 ° C. of 2.0 to 8.0 mm ² / s and an aromatic content of 10% by mass or less. The base oil component may comprise a plurality of base oil components.

When the lubricating oil composition is a multigrade oil, the content of the lubricating base oil according to the present embodiment in the lubricating oil composition of the present invention is usually 70% by mass or more based on the total amount of the lubricating oil composition. Yes, preferably 75% by mass or more, more preferably 80% by mass or more, and usually 90% by mass or less. When the lubricating oil composition is a single grade oil, it is usually 80% by mass or more, preferably 85% by mass or more, more preferably 90% by mass or more, based on the total amount of the lubricating oil composition. It is 95 mass% or less.

<(B) Metal-based detergent>
The lubricating oil composition of the present invention has (B) a metallic detergent (hereinafter referred to as “component (B)”) as a (B) metallic detergent (hereinafter referred to as “component (B)”). And (B2) a metal detergent overbased with magnesium carbonate (hereinafter also referred to as “(B2) component”). Examples of the component (B) include phenate detergents, sulfonate detergents, and salicylate detergents. Moreover, these metal type detergents can be used individually or in combination of 2 or more types.

Preferred examples of the phenate detergent include an overbased salt of an alkaline earth metal salt of a compound having a structure represented by the following formula (1). Examples of the alkaline earth metal include magnesium, barium, and calcium. Among these, magnesium or calcium is preferable.

In the formula (1), R ¹ represents a linear or branched chain having 6 to 21 carbon atoms, a saturated or unsaturated alkyl group or alkenyl group, m represents the degree of polymerization and represents an integer of 1 to 10, Represents a sulfide (—S—) group or a methylene (—CH ₂ —) group, and x represents an integer of 1 to 3. R ¹ may be a combination of two or more different groups.

The number of carbon atoms of R ¹ in the formula (1) is preferably 9-18, more preferably 9-15. If the carbon number of R ¹ is less than 6, the solubility in the base oil may be poor. On the other hand, if the carbon number of R ¹ exceeds 21, the production may be difficult and the heat resistance may be poor.

The degree of polymerization m in the formula (1) is preferably 1 to 4. When the degree of polymerization m is within this range, the heat resistance can be increased.

Preferred examples of the sulfonate detergent include an alkaline earth metal salt of an alkyl aromatic sulfonic acid obtained by sulfonating an alkyl aromatic compound, or a basic salt or an overbased salt thereof. The weight average molecular weight of the alkyl aromatic compound is preferably 400 to 1500, more preferably 700 to 1300.
Examples of the alkaline earth metal include magnesium, barium, and calcium, and magnesium or calcium is preferable. Examples of the alkyl aromatic sulfonic acid include so-called petroleum sulfonic acid and synthetic sulfonic acid. As petroleum sulfonic acid here, what sulfonated the alkyl aromatic compound of the lubricating oil fraction of mineral oil, what is called mahoganic acid etc. byproduced at the time of white oil manufacture are mentioned. In addition, as an example of synthetic sulfonic acid, linear or branched alkyl obtained by recovering a by-product in an alkylbenzene production plant that is a raw material of a detergent or by alkylating benzene with polyolefin Examples include sulfonated alkylbenzene having a group. Another example of the synthetic sulfonic acid is a sulfonated alkyl naphthalene such as dinonylnaphthalene. Moreover, there is no restriction | limiting in particular as a sulfonating agent at the time of sulfonating these alkyl aromatic compounds, For example, fuming sulfuric acid and anhydrous sulfuric acid can be used.

Preferred examples of the salicylate detergent include metal salicylate or a basic salt or an overbased salt thereof. Preferred examples of the metal salicylate here include compounds represented by the following formula (2).

In the above formula (2), R ² each independently represents an alkyl group or alkenyl group having 14 to 30 carbon atoms, M represents an alkaline earth metal, and n represents 1 or 2. M is preferably calcium or magnesium. n is preferably 1. When n = 2, R ² may be a combination of different groups.

As a preferred embodiment of the salicylate detergent, there can be mentioned alkaline earth metal salicylate in which n = 1 in the above formula (2), or a basic salt or an overbased salt thereof.

The production method of the alkaline earth metal salicylate is not particularly limited, and a known production method of monoalkyl salicylate can be used. For example, monoalkyl salicylic acid obtained by alkylation with olefin using phenol as a starting material and then carboxylation with carbon dioxide gas or the like, or alkylation with an equivalent amount of the above olefin using salicylic acid as a starting material. The obtained monoalkyl salicylic acid or the like is reacted with a metal base such as an alkaline earth metal oxide or hydroxide, or these monoalkyl salicylic acid or the like is once converted into an alkali metal salt such as a sodium salt or a potassium salt. Alkaline earth metal salicylate can be obtained by exchanging metal with an alkaline earth metal salt.

The method for obtaining an alkaline earth metal phenate, sulfonate, or salicylate overbased with calcium carbonate or magnesium carbonate is not particularly limited. For example, an alkaline earth metal phenate, sulfonate, Alternatively, it can be obtained by reacting salicylate with a base such as calcium hydroxide or magnesium hydroxide.

The metal ratio of the component (B) is a value calculated according to the following formula, preferably 1 or more, more preferably 2 or more, and particularly preferably 3 or more. Further, it is preferably 50 or less, more preferably 30 or less, and particularly preferably 10 or less.
(B) component metal ratio = valence of metal element in component (B) × metal content of component (B) (mol) / soap group content of component (B) (mol)

As the component (B1), for example, a calcium phenate detergent, a calcium sulfonate detergent, a calcium salicylate detergent, or a combination thereof, which is overbased with calcium carbonate, can be used. The component (B1) preferably contains at least a calcium salicylate detergent.

As the component (B2), for example, a magnesium phenate detergent, a magnesium sulfonate detergent, a magnesium salicylate detergent, or a combination thereof, which is overbased with magnesium carbonate, can be used. The component (B2) preferably contains at least a magnesium salicylate detergent or a magnesium sulfonate detergent.

The content of the component (B1) in the lubricating oil composition is such that the calcium content in the lubricating oil composition is 1500 ppm by mass or less, preferably 1400-1500 ppm by mass based on the total amount of the lubricating oil composition. . When the calcium content exceeds 1500 ppm by mass, LSPI tends to occur. Further, when the calcium content is not less than the above lower limit value, the cleanliness inside the engine can be kept high and the base number maintainability is also improved.
The content of the component (B2) in the lubricating oil composition is such that the magnesium content in the lubricating oil composition is 300 ppm by mass or more, preferably 350 to 600 ppm by mass, based on the total amount of the lubricating oil composition. . When the magnesium content is equal to or higher than the lower limit, engine cleanliness can be improved while suppressing LSPI. Moreover, when a magnesium content is below the said upper limit, the raise of a friction coefficient can be suppressed.

<(C) Molybdenum friction modifier (MoDTC)>
The lubricating oil composition of the present invention contains molybdenum sulfide dithiocarbamate or sulfurized oxymolybdenum dithiocarbamate (hereinafter sometimes referred to as “component (C)”) as a molybdenum-based friction modifier. As the component (C), for example, a compound represented by the following formula (3) can be used.

In the general formula (3), R ³ to R ⁶ may be the same or different, and are each an alkyl group having 2 to 24 carbon atoms or an (alkyl) aryl group having 6 to 24 carbon atoms, preferably 4 carbon atoms. Or an alkyl group having 13 to 13 carbon atoms or an (alkyl) aryl group having 10 to 15 carbon atoms. The alkyl group may be any of a primary alkyl group, a secondary alkyl group, and a tertiary alkyl group, and may be linear or branched. The “(alkyl) aryl group” means “aryl group or alkylaryl group”. In the alkylaryl group, the substitution position of the alkyl group in the aromatic ring is arbitrary. Y ¹ to Y ⁴ are each independently a sulfur atom or an oxygen atom, and at least one of Y ¹ to Y ⁴ is a sulfur atom.

The content of the component (C) in the lubricating oil composition is such that the molybdenum content in the lubricating oil composition is 600 ppm by mass or more, preferably 700 ppm by mass or more based on the total amount of the lubricating oil composition, and preferably The amount is 1000 mass ppm or less, more preferably 900 mass ppm or less, still more preferably 850 mass ppm or less, and particularly preferably 800 mass ppm or less. When the molybdenum content is equal to or higher than the lower limit, fuel economy and LSPI suppression can be improved. Moreover, the storage stability of a lubricating oil composition can be improved because molybdenum content is always below an upper limit.

<(D) Antioxidant>
The lubricating oil composition of the present invention may contain an amine-based antioxidant and / or a phenol-based antioxidant (hereinafter sometimes referred to as “component (D)”) as (D) an antioxidant. preferable. As the amine-based antioxidant, for example, known amine-based antioxidants such as alkylated diphenylamine, alkylated phenyl-α-naphthylamine, phenyl-α-naphthylamine, and phenyl-β-naphthylamine can be used without particular limitation. Examples of phenolic antioxidants include known phenols such as 2,6-di-tert-butyl-4-methylphenol (DBPC) and 4,4′-methylenebis (2,6-di-tert-butylphenol). A system antioxidant can be used without particular limitation. When the antioxidant is contained in the lubricating oil composition of the present invention, the content is usually 0.1 to 5% by mass based on the total amount of the lubricating oil composition.

The lubricating oil composition of the present invention preferably contains an amine-based antioxidant as the component (D). When the amine-based antioxidant is contained in the lubricating oil composition of the present invention, the content thereof is preferably 0.01 to 0.1% by mass as the nitrogen amount based on the total amount of the lubricating oil composition. When the content of the amine-based antioxidant as the amount of nitrogen is not less than the above lower limit, the life performance of the lubricating oil can be further enhanced. Further, when the content of the amine-based antioxidant as the amount of nitrogen is not more than the above upper limit value, colored stains inside the engine can be suppressed.

<(E) Zinc dialkyldithiophosphate>
The lubricating oil composition of the present invention preferably contains (E) zinc dialkyldithiophosphate (ZnDTP; hereinafter sometimes referred to as “component (E)”). As the component (E), for example, a compound represented by the following formula (4) can be used.

In the formula (4), R ⁷ to R ¹⁰ each independently represent a linear or branched alkyl group having 1 to 24 carbon atoms, and may be a combination of different groups. The carbon number of R ⁷ to R ¹⁰ is preferably 3 or more, preferably 12 or less, more preferably 8 or less. R ⁷ to R ¹⁰ may be any of a primary alkyl group, a secondary alkyl group, and a tertiary alkyl group, but a primary alkyl group, a secondary alkyl group, or a group thereof. A combination is preferred, and the molar ratio of the primary alkyl group to the secondary alkyl group (primary alkyl group: secondary alkyl group) is preferably 0: 100 to 30:70. . This ratio may be a combination ratio of alkyl chains in the molecule, or a mixture ratio of ZnDTP having only primary alkyl groups and ZnDTP having only secondary alkyl groups. Since the secondary alkyl group is mainly used, it is possible to improve fuel efficiency.

The method for producing the zinc dialkyldithiophosphate is not particularly limited. For example, it can be synthesized by reacting an alcohol having an alkyl group corresponding to R ⁷ to R ¹⁰ with diphosphorus pentasulfide to synthesize dithiophosphoric acid and neutralizing it with zinc oxide.

When the lubricating oil composition (E) component of the present invention is contained, the content thereof is preferably 0.03 to 1.0% by mass based on the total amount of the composition. The content of component (E) is preferably such that the phosphorus content in the lubricating oil composition is 750 to 800 ppm by mass based on the total amount of the lubricating oil composition. When the phosphorus content in the lubricating oil composition is not less than the above lower limit value, not only the oxidation stability can be enhanced, but also the LSPI suppression ability can be enhanced. Moreover, when the phosphorus content in the lubricating oil composition is not more than the above upper limit, it is possible to avoid a decrease in base number due to hydrolysis of zinc dithiophosphate.

<(F) Corrosion inhibitor or metal deactivator>
The lubricating oil composition of the present invention preferably contains (F) a corrosion inhibitor or a metal deactivator (hereinafter sometimes referred to as “component (F)”). Examples of the component (F) include known corrosion inhibitors such as benzotriazole, tolyltriazole, thiadiazole, and imidazole compounds, imidazolines, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles and derivatives thereof. 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bisdialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, β- (o-carboxybenzylthio) propiononitrile, etc. A known metal deactivator can be used without particular limitation. When the component (F) is contained in the lubricating oil composition of the present invention, the content thereof is usually 0.005 to 5% by mass based on the total amount of the composition.

In the lubricating oil composition of the present invention, it is preferable to use a compound containing sulfur as the component (F). Preferable examples of the corrosion inhibitor or metal deactivator that is a sulfur-containing compound include, for example, thiadiazole. By using a sulfur-containing compound as the component (F), it is possible to further enhance the LSPI suppression ability and to more effectively bring out the friction reduction effect of the component (C) that is a molybdenum-based friction modifier. . When the lubricating oil composition of the present invention contains a sulfur-containing compound as a corrosion inhibitor or metal deactivator, the content is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably Is 0.1% by mass or more, and is usually 1.0% by mass or less, preferably 0.5% by mass or less, more preferably 0.3% by mass or less.

The sulfur content in the lubricating oil composition is preferably 0.20 to 0.30 mass%, more preferably 0.23 to 0.28 mass%, based on the total amount of the lubricating oil composition. When the sulfur content in the lubricating oil composition is not less than the above lower limit value, the LSPI suppression ability can be further enhanced, and the friction reducing effect of the component (C) which is a molybdenum friction modifier is more effectively achieved. It can be pulled out. Further, when the sulfur content in the lubricating oil composition is not more than the above upper limit value, the engine cleanliness can be kept high.

<(G) Nitrogen-containing ashless dispersant>
The lubricating oil composition of the present invention may contain (G) a nitrogen-containing ashless dispersant (hereinafter sometimes referred to as “(G) component”).
As the component (G), for example, one or more compounds selected from the following (G-1) to (G-3) can be used.
(G-1) Succinimide having at least one alkyl group or alkenyl group in the molecule or a derivative thereof (hereinafter sometimes referred to as “component (G-1)”),
(G-2) benzylamine or a derivative thereof having at least one alkyl group or alkenyl group in the molecule (hereinafter sometimes referred to as “component (G-2)”),
(G-3) A polyamine having at least one alkyl group or alkenyl group in the molecule or a derivative thereof (hereinafter sometimes referred to as “component (G-3)”).

As the component (G), the component (G-1) can be particularly preferably used.
Among the components (G-1), examples of the succinimide having at least one alkyl group or alkenyl group in the molecule include compounds represented by the following formula (5) or formula (6).

In the formula (5), R ¹¹ represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, and h represents an integer of 1 to 5, preferably 2 to 4. R ¹¹ preferably has 60 or more carbon atoms, and more preferably 350 or less.

In the formula (6), R ¹² and R ¹³ each independently represent an alkyl group or alkenyl group having 40 to 400 carbon atoms, and may be a combination of different groups. R ¹² and R ¹³ are particularly preferably a polybutenyl group. I represents an integer of 0 to 4, preferably 1 to 3. R ¹² and R ¹³ preferably have 60 or more carbon atoms, and more preferably 350 or less.

When the carbon number of R ¹¹ to R ¹³ in the formulas (5) and (6) is not less than the above lower limit value, good solubility in the lubricating base oil can be obtained. On the other hand, when the carbon number of R ¹¹ to R ¹³ is equal to or less than the upper limit, the low temperature fluidity of the lubricating oil composition can be improved.

The alkyl group or alkenyl group (R ¹¹ to R ¹³ ) in the formulas (5) and (6) may be linear or branched, and is preferably an olefin oligomer such as propylene, 1-butene, isobutene, etc. And a branched alkyl group and a branched alkenyl group derived from a co-oligomer of ethylene and propylene. Of these, branched alkyl groups or alkenyl groups derived from oligomers of isobutene conventionally called polyisobutylene, and polybutenyl groups are most preferred.
The preferred number average molecular weight of the alkyl group or alkenyl group (R ¹¹ to R ¹³ ) in the formulas (5) and (6) is 800 to 3500.

The succinimide having at least one alkyl group or alkenyl group in the molecule is a so-called monotype succinimide represented by the formula (5) in which succinic anhydride is added only to one end of the polyamine chain. And a so-called bis-type succinimide represented by formula (6) in which succinic anhydride is added to both ends of the polyamine chain. Either the monotype succinimide and the bis type succinimide may be contained in the lubricating oil composition of the present invention, or both of them may be contained as a mixture.

The method for producing a succinimide having at least one alkyl group or alkenyl group in the molecule is not particularly limited. For example, a compound having an alkyl group or alkenyl group having 40 to 400 carbon atoms and maleic anhydride and 100 Alkyl succinic acid or alkenyl succinic acid obtained by reaction at ˜200 ° C. can be obtained by reacting with polyamine. Here, examples of the polyamine include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

Among the components (G-2), examples of the benzylamine having at least one alkyl group or alkenyl group in the molecule include compounds represented by the following formula (7).

In the formula (7), R ¹⁴ represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, and j represents an integer of 1 to 5, preferably 2 to 4. R ¹⁴ preferably has 60 or more carbon atoms, and more preferably 350 or less.

The production method of component (G-2) is not particularly limited. For example, a polyolefin such as propylene oligomer, polybutene, or ethylene-α-olefin copolymer is reacted with phenol to form alkylphenol, and then formaldehyde, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine The method of making it react with polyamines, such as a Mannich reaction, is mentioned.

Examples of the polyamine having at least one alkyl group or alkenyl group in the component (G-3) include compounds represented by the following formula (8).

In the formula (8), R ¹⁵ represents an alkyl group or an alkenyl group having 40 to 400 carbon atoms, and k represents an integer of 1 to 5, preferably 2 to 4. R ¹⁵ preferably has 60 or more carbon atoms, and more preferably 350 or less.

The production method of component (G-3) is not particularly limited. For example, after chlorinating a polyolefin such as a propylene oligomer, polybutene or ethylene-α-olefin copolymer, this is reacted with a polyamine such as ammonia, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine or pentaethylenehexamine. A method is mentioned.

Examples of the derivatives in the component (G-1) to the component (G-3) include (i) succinimide, benzylamine or polyamine (hereinafter referred to as “above-mentioned”) having at least one alkyl group or alkenyl group in the molecule. A monocarboxylic acid having 1 to 30 carbon atoms, such as a fatty acid, and a polycarboxylic acid having 2 to 30 carbon atoms (for example, oxalic acid, phthalic acid, trimellitic acid, pyromellitic acid, etc.). In addition, by reacting these anhydrides or ester compounds, alkylene oxides having 2 to 6 carbon atoms, or hydroxy (poly) oxyalkylene carbonate, some or all of the remaining amino groups and / or imino groups are neutralized. Or an amidated modified compound with an oxygen-containing organic compound; (ii) action of boric acid on the above-mentioned nitrogen-containing compound A boron-modified compound in which part or all of the remaining amino group and / or imino group is neutralized or amidated; (iii) by reacting phosphoric acid with the nitrogen-containing compound described above, A phosphoric acid-modified compound in which a part or all of the amino group and / or imino group is neutralized or amidated; (iv) a sulfur-modified compound obtained by allowing a sulfur compound to act on the nitrogen-containing compound described above And (v) a modified compound obtained by combining the above-mentioned nitrogen-containing compound with two or more kinds of modifications selected from modification with an oxygen-containing organic compound, boron modification, phosphoric acid modification, and sulfur modification. . Among these derivatives (i) to (v), by using a boric acid-modified compound of alkenyl succinimide, particularly a boric acid-modified compound of bis-type alkenyl succinimide, the heat resistance of the lubricating oil composition can be further improved. Can be improved.

The molecular weight of the component (G) is not particularly limited, but a suitable weight average molecular weight is 1000 to 20000.

When the component (G) is contained in the lubricating oil composition of the present invention, the content is preferably 0.01% by mass or more, more preferably 0.03 as nitrogen content, based on the total amount of the lubricating oil composition. It is at least 0.1% by mass, preferably at most 0.15% by mass, more preferably at most 0.1% by mass, particularly preferably at most 0.07% by mass. When the content of the component (G) is not less than the above lower limit, the coking resistance (heat resistance) of the lubricating oil composition can be sufficiently improved. Moreover, when the content of the component (G) is equal to or less than the above upper limit value, fuel economy can be maintained high.

The boron content in the lubricating oil composition is preferably 0 ppm by mass or more, more preferably 100 ppm by mass or more, and particularly preferably 200 ppm by mass or more based on the total amount of the lubricating oil composition. Moreover, Preferably it is less than 400 mass ppm, More preferably, it is 350 mass ppm, Especially preferably, it is 300 mass ppm. When the boron content is not more than the above upper limit value, fuel economy can be maintained high, and the ash content of the lubricating oil composition can be kept low.

<(H) Viscosity index improver>
The lubricating oil composition of the present invention preferably contains (H) a viscosity index improver (hereinafter sometimes referred to as “component (H)”). Examples of component (H) include non-dispersed or dispersed poly (meth) acrylate viscosity index improvers, (meth) acrylate-olefin copolymers, non-dispersed or dispersed ethylene-α-olefin copolymers. Or a hydride thereof, polyisobutylene or a hydride thereof, a styrene-diene hydrogenated copolymer, a styrene-maleic anhydride ester copolymer, and a polyalkylstyrene.

The component (H) is a poly (meth) acrylate viscosity index improver (hereinafter referred to as the proportion of structural units represented by the following general formula (9) in the total monomer units in the polymer of 10 to 90 mol%) It is preferable to contain “sometimes referred to as a viscosity index improver according to this embodiment”.

[In the formula (9), R ¹⁶ represents hydrogen or a methyl group, and R ¹⁷ represents a linear or branched hydrocarbon group having 1 to 5 carbon atoms. ]

In the viscosity index improver according to this embodiment, the proportion of the (meth) acrylate structural unit represented by the general formula (9) in the polymer is preferably 10 to 90 mol%, more preferably 80 mol% or less. More preferably, it is 70 mol% or less. More preferably, it is 20 mol% or more, More preferably, it is 30 mol% or more, Especially preferably, it is 40 mol% or more. When the proportion of the (meth) acrylate structural unit represented by the general formula (9) in all the monomer units in the polymer exceeds 90 mol%, the effect of improving solubility in the base oil and viscosity temperature characteristics There exists a possibility that it may be inferior to a low temperature viscosity characteristic, and when it is less than 10 mol%, there exists a possibility that it may be inferior to the improvement effect of a viscosity temperature characteristic.

The viscosity index improver according to the present embodiment may be a copolymer having another (meth) acrylate structural unit in addition to the (meth) acrylate structural unit represented by the general formula (9). Such a copolymer includes one or more monomers represented by the following general formula (10) (hereinafter referred to as “monomer (M-1)”) and other than the monomer (M-1). It can be obtained by copolymerizing with a monomer.

[In the formula (10), R ¹⁸ represents a hydrogen atom or a methyl group, and R ¹⁹ represents a linear or branched hydrocarbon group having 6 to 18 carbon atoms. ]

The monomer to be combined with the monomer (M-1) is arbitrary, but for example, a monomer represented by the following general formula (11) (hereinafter referred to as “monomer (M-2)”) is preferable. The copolymer of the monomer (M-1) and the monomer (M-2) is a so-called non-dispersed poly (meth) acrylate viscosity index improver.

[In the formula (11), R ²⁰ represents a hydrogen atom or a methyl group, and R ²¹ represents a linear or branched hydrocarbon group having 19 or more carbon atoms. ]

R ²¹ in the monomer (M-2) represented by the formula (11) is a straight chain or branched hydrocarbon group having 19 or more carbon atoms as described above, and preferably a straight chain having 20 or more carbon atoms. Or it is a branched hydrocarbon, More preferably, it is a linear or branched hydrocarbon with 22 or more carbon atoms, More preferably, it is a branched hydrocarbon group with 24 or more carbon atoms. The upper limit of the carbon number of the hydrocarbon group represented by R ²¹ is not particularly limited, but is preferably a linear or branched hydrocarbon group having a carbon number of 50,000 or less. More preferably, it is a linear or branched hydrocarbon group of 500 or less, more preferably a linear or branched hydrocarbon group of 100 or less, particularly preferably 50 or less. A hydrocarbon group, most preferably a branched hydrocarbon group of 25 or less.

As a preferred example of the viscosity index improver according to the present embodiment, comb-shaped poly (meth) acrylate can be exemplified. The comb-shaped poly (meth) acrylate here is a copolymer of the monomer (M-1) and the monomer (M-2), and the monomer (M-2) is R ²¹ in the formula (11). Means a copolymer having a number average molecular weight (Mn) of 1,000 to 50,000 (preferably 1,500 to 20,000, more preferably 2,000 to 10,000). . As such a macromonomer, for example, a macromonomer derived from a hydride of polyolefin obtained by copolymerizing butadiene and isoprene can be employed.

In the viscosity index improver according to this embodiment, the number of (meth) acrylate structural units corresponding to the monomer (M-2) represented by the general formula (11) in the polymer may be one, or two A combination of the above may be used. The proportion of the structural unit corresponding to the monomer (M-2) represented by the general formula (11) in the total monomer units in the polymer is preferably 0.5 to 70 mol%, more preferably It is 60 mol% or less, more preferably 50 mol% or less, particularly preferably 40 mol% or less, and most preferably 30 mol% or less. Further, it is preferably 1 mol% or more, more preferably 3 mol% or more, further preferably 5 mol% or more, and particularly preferably 10 mol% or more. When the proportion of the structural unit corresponding to the monomer (M-2) represented by the general formula (11) in the total monomer units in the polymer exceeds 70 mol%, the effect of improving the viscosity temperature characteristics and the low temperature viscosity characteristics If the amount is less than 0.5 mol%, the effect of improving the viscosity temperature characteristic may be inferior.

Other monomers to be combined with the monomer (M-1) include a monomer represented by the following general formula (12) (hereinafter referred to as “monomer (M-3)”) and a general formula (13). One or more selected from monomers (hereinafter referred to as “monomer (M-4)”) are preferred. The copolymer of the monomer (M-1) and the monomer (M-3) and / or (M-4) is a so-called dispersion type poly (meth) acrylate viscosity index improver. The dispersion type poly (meth) acrylate viscosity index improver may further contain a monomer (M-2) as a constituent monomer.

[In the formula (12), R ²² represents a hydrogen atom or a methyl group, R ²³ represents an alkylene group having 1 to 18 carbon atoms, E ¹ represents 1 to 2 nitrogen atoms and 0 to 2 oxygen atoms. Represents an amine residue or a heterocyclic residue, and a represents 0 or 1; ]

Specific examples of the alkylene group having 1 to 18 carbon atoms represented by R ²³ include ethylene group, propylene group, butylene group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group, Examples include an undecylene group, a dodecylene group, a tridecylene group, a tetradecylene group, a pentadecylene group, a hexadecylene group, a heptadecylene group, and an octadecylene group (these alkylene groups may be linear or branched).

Specific examples of the group represented by E ¹ include a dimethylamino group, a diethylamino group, a dipropylamino group, a dibutylamino group, an anilino group, a toluidino group, a xylidino group, an acetylamino group, a benzoylamino group, and a morpholino group. Pyrrolyl group, pyrrolino group, pyridyl group, methylpyridyl group, pyrrolidinyl group, piperidinyl group, quinonyl group, pyrrolidonyl group, pyrrolidono group, imidazolino group, pyrazino group and the like.

[In the formula (13), R ²⁴ represents a hydrogen atom or a hydrocarbon group, E ² represents an amine residue or heterocyclic residue containing 1 to 2 hydrocarbon groups or nitrogen atoms and 0 to 2 oxygen atoms. Represents a group. ]

Specific examples of the group represented by E ² include a dimethylamino group, a diethylamino group, a dipropylamino group, a dibutylamino group, an anilino group, a toluidino group, a xylidino group, an acetylamino group, a benzoylamino group, and a morpholino group. Pyrrolyl group, pyrrolino group, pyridyl group, methylpyridyl group, pyrrolidinyl group, piperidinyl group, quinonyl group, pyrrolidonyl group, pyrrolidono group, imidazolino group, pyrazino group and the like.

As preferable examples of the monomers (M-3) and (M-4), specifically, dimethylaminomethyl methacrylate, diethylaminomethyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 2-methyl-5-vinylpyridine, Examples thereof include morpholinomethyl methacrylate, morpholinoethyl methacrylate, N-vinylpyrrolidone, and mixtures thereof.

There is no particular limitation on the copolymerization molar ratio of the copolymer of monomer (M-1) and monomers (M-2) to (M-4), but monomer (M-1): monomer (M-2) (M-4) = 20: 80 to 90:10 is preferable, more preferably 30:70 to 80:20, and still more preferably 40:60 to 70:30.

The method for producing the viscosity index improver according to the present embodiment is arbitrary. For example, in the presence of a polymerization initiator such as benzoyl peroxide, the monomer (M-1) and / or (M-2) and the monomer It can be easily obtained by radical solution polymerization of one or more selected from (M-3) to (M-4).

The PSSI (Permanent Shear Stability Index) in the diesel injector method of the viscosity index improver according to this embodiment is preferably 40 or less, more preferably 10 or less, still more preferably 5 or less, particularly preferably 3 or less, most. Preferably it is 1 or less. When PSSI exceeds 40, the shear stability is poor, and the kinematic viscosity after use and the HTHS viscosity are kept at a certain level or more, so that the initial fuel economy may be deteriorated. The lower limit of PSSI of the viscosity index improver according to this embodiment is not particularly limited, but is usually more than zero. In this specification, “PSSI” refers to ASTM D 6022-01 (Standard Practice for Calculation of Permanent Shear Stability Index), and ASTM D 6278-02 (Test Method for Shear Stability of Polymer Containing Fluids European European It means the permanent shear stability index (Permanent 基づき Shear Stability Index) calculated based on data measured by Diesel Injector Apparatus.

The weight average molecular weight (Mw) of the viscosity index improver according to this embodiment is usually 10,000 to 700,000, preferably 20,000 or more, more preferably 50,000 or more, Preferably it is 100,000 or more, Most preferably, it is 120,000 or more. Moreover, it is preferably 500,000 or less, more preferably 400,000 or less, and still more preferably 300,000 or less. If the weight average molecular weight is less than 10,000, the effect of improving the viscosity index when dissolved in a lubricating base oil is small, resulting in poor fuel economy and low temperature viscosity characteristics, and may increase costs. Further, when the weight average molecular weight exceeds 700,000, the effect of increasing the viscosity becomes too large, and not only the fuel saving property and the low temperature viscosity property are inferior, but also shear stability, solubility in lubricating base oil, and storage. Stability deteriorates.

The ratio (Mw / PSSI) of the weight average molecular weight and the PSSI of the viscosity index improver according to this embodiment is preferably 1.0 × 10 ⁴ or more, more preferably 2.0 × 10 ⁴ or more, and still more preferably. Is 5.0 × 10 ⁴ or more, and particularly preferably 8.0 × 10 ⁴ or more. When Mw / PSSI is less than 1.0 × 10 ⁴ , fuel economy and low temperature startability, that is, viscosity temperature characteristics and low temperature viscosity characteristics may be deteriorated.

The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the viscosity index improver according to this embodiment is preferably 4.0 or less, more preferably 3.5 or less, It is preferably 3.0 or less, particularly preferably 2.0 or less, and most preferably 1.5 or less. Moreover, it is preferable that Mw / Mn is 1.0 or more, More preferably, it is 1.05 or more, More preferably, it is 1.1 or more. When Mw / Mn exceeds 4.0, the effect of improving the solubility and the viscosity-temperature characteristic deteriorates, so that sufficient storage stability and fuel economy may not be maintained.

The content of the component (H) in the lubricating oil composition of the present invention is usually 0.1 to 30% by mass, preferably 1% by mass or more, more preferably 3%, based on the total amount of the composition, including diluted oil. It is at least 5 mass%, more preferably at least 5 mass%, preferably at most 20 mass%, more preferably at most 15 mass%. When the content is less than 0.1% by mass, the fuel efficiency is deteriorated and the low temperature characteristics may be insufficient. When the content exceeds 30% by mass, the fuel efficiency of the composition is decreased. May deteriorate and shear stability may deteriorate.

<Other additives>
In order to further improve the performance, the lubricating oil composition of the present invention can contain other additives generally used in lubricating oils depending on the purpose. Examples of such additives include additives such as friction modifiers other than the component (C), antiwear agents (or extreme pressure agents), rust inhibitors, demulsifiers, antifoaming agents, and the like. .

As the friction modifier other than the component (C), for example, one or more friction modifiers selected from organic molybdenum compounds other than the component (C) and ashless friction modifiers can be used. The content of the friction modifier other than the component (C) is preferably 0.01 to 2.0% by mass based on the total amount of the composition. By containing a friction modifier other than the component (C), the fuel saving performance can be further enhanced.

Examples of organic molybdenum compounds other than the component (C) include molybdenum dithiophosphate; molybdenum compounds (for example, molybdenum oxide such as molybdenum dioxide and molybdenum trioxide, orthomolybdic acid, paramolybdic acid, and (poly) sulfurized molybdenum acid). Molybdenum acid, metal salts of these molybdates, molybdates such as ammonium salts, molybdenum disulfide, molybdenum trisulfide, molybdenum pentasulfide, molybdenum sulfide such as polysulfide molybdenum, molybdenum sulfides, metal salts of molybdenum sulfides or amines Salts, molybdenum halides such as molybdenum chloride, etc.) and sulfur-containing organic compounds (eg alkyl (thio) xanthate, thiadiazole, mercaptothiadiazole, thiocarbonate, tetrahydrocarbyl thiuram disulfide) Bis (di (thio) hydrocarbyl dithiophosphonate) disulfide, organic (poly) sulfide, sulfurized ester, etc.) or other organic compounds, etc .; and sulfur-containing molybdenum compounds such as molybdenum sulfide and sulfurized molybdate And organic molybdenum compounds containing sulfur, such as a complex of alkenyl succinimide and alkenyl succinimide. The organic molybdenum compound may be a mononuclear molybdenum compound or a polynuclear molybdenum compound such as a dinuclear molybdenum compound or a trinuclear molybdenum compound.

Also, as the organic molybdenum compound other than the component (C), an organic molybdenum compound not containing sulfur as a constituent element can be used. Specific examples of organic molybdenum compounds that do not contain sulfur as a constituent element include molybdenum-amine complexes, molybdenum-succinimide complexes, molybdenum salts of organic acids, and molybdenum salts of alcohols. Complexes, molybdenum salts of organic acids and molybdenum salts of alcohols are preferred.

When using an organomolybdenum compound as a friction modifier other than the component (C), the content is preferably 0.01 to 2.0% by mass based on the total amount of the composition. (C) Even when an organomolybdenum compound is included as a friction modifier other than the component, the molybdenum content in the lubricating oil composition is 600 mass ppm or more, preferably 700 mass ppm or more, based on the total amount of the lubricating oil composition. Further, it is preferably 1000 ppm by mass or less, more preferably 900 ppm by mass or less, further preferably 850 ppm by mass or less, and particularly preferably 800 ppm by mass or less. When the content is less than the above lower limit, the friction reducing effect due to the addition tends to be insufficient, and the fuel economy and thermal / oxidation stability of the lubricating oil composition tend to be insufficient. On the other hand, when content exceeds the said upper limit, the effect corresponding to content is not acquired, and it exists in the tendency for the storage stability of a lubricating oil composition to fall.

As the ashless friction modifier, a compound usually used as a friction modifier for lubricating oils can be used without particular limitation. As an ashless friction modifier, for example, a compound having 6 to 50 carbon atoms containing one or more hetero elements selected from an oxygen atom, a nitrogen atom and a sulfur atom in the molecule can be mentioned. More specifically, at least one alkyl group or alkenyl group having 6 to 30 carbon atoms, particularly a straight chain alkyl group, straight chain alkenyl group, branched alkyl group, or branched alkenyl group having 6 to 30 carbon atoms in the molecule. Examples thereof include ashless friction modifiers such as amine compounds, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, aliphatic ethers, urea compounds, hydrazide compounds, and the like.

When the lubricating oil composition contains an ashless friction modifier, the content is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and still more preferably, based on the total amount of the lubricating oil composition. Is 0.3% by mass or more, preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.8% by mass or less. If the content of the ashless friction modifier is less than 0.01% by mass, the effect of reducing friction due to the addition tends to be insufficient, and if it exceeds 2% by mass, the effect of an anti-wear additive or the like. Tends to be inhibited, or the solubility of the additive tends to deteriorate.

As the antiwear agent (or extreme pressure agent), the antiwear agent / extreme pressure agent used in the lubricating oil can be used without particular limitation. For example, sulfur-based, phosphorus-based, sulfur-phosphorus extreme pressure agents and the like can be used. Specifically, phosphites, thiophosphites, dithiophosphites, trithiophosphites Esters, phosphate esters, thiophosphate esters, dithiophosphate esters, trithiophosphate esters, amine salts thereof, metal salts thereof, derivatives thereof, dithiocarbamates, zinc dithiocarbamates, disulfides, polysulfides , Sulfurized olefins, sulfurized fats and oils, and the like. Among these, addition of a sulfur-based extreme pressure agent is preferable, and sulfurized fats and oils are particularly preferable. When the lubricant composition contains an antiwear agent (or extreme pressure agent), the content is preferably 0.01 to 10% by mass based on the total amount of the lubricant composition.

Examples of the rust preventive include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinate, and polyhydric alcohol ester. When the lubricating oil composition contains a rust inhibitor, the content thereof is preferably 0.01 to 10% by mass based on the total amount of the lubricating oil composition.

Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthyl ether. When the anti-emulsifier is included in the lubricating oil composition, the content is preferably 0.01 to 10% by mass based on the total amount of the lubricating oil composition.

Examples of antifoaming agents include silicone oils having a kinematic viscosity at 25 ° C. of 1000 to 100,000 mm ² / s, alkenyl succinic acid derivatives, esters of polyhydroxy aliphatic alcohols and long chain fatty acids, methyl salicylates, and , O-hydroxybenzyl alcohol and the like. When the antifoaming agent is included in the lubricating oil composition, the content is preferably 0.01 to 10% by mass based on the total amount of the lubricating oil composition.

<Lubricating oil composition>
The kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is preferably 4.0 to 12 mm ² / s, more preferably 9.3 mm ² / s or less, and still more preferably 8.2 mm ² / s or less. Particularly preferably, it is 7.1 mm ² / s or less, and most preferably 6.8 mm ² / s or less. Further, it is more preferably 5.0 mm ² / s or more, further preferably 5.5 mm ² / s or more, particularly preferably 6.1 mm ² / s or more, and most preferably 6.3 mm ² / s or more. If the kinematic viscosity at 100 ° C. of the lubricating oil composition is less than 4.0 mm ² / s, there is a risk of insufficient lubricity. If it exceeds 12 mm ² / s, the necessary low temperature viscosity and sufficient fuel saving Performance may not be obtained.

The kinematic viscosity at 40 ° C. of the lubricating oil composition of the present invention is preferably 4.0 to 50 mm ² / s, more preferably 40 mm ² / s or less, still more preferably 35 mm ² / s or less, further preferably It is 32 mm ² / s or less, particularly preferably 30 mm ² / s or less, and most preferably 28 mm ² / s or less. Further, it is more preferably 15 mm ² / s or more, further preferably 18 mm ² / s or more, still more preferably 20 mm ² / s or more, particularly preferably 22 mm ² / s or more, and most preferably 25 mm ² / s or more. When the kinematic viscosity at 40 ° C. of the lubricating oil composition is less than 4 mm ² / s, there is a risk of insufficient lubricity, and when it exceeds 50 mm ² / s, the necessary low temperature viscosity and sufficient fuel saving performance are obtained. May not be obtained.

The viscosity index of the lubricating oil composition of the present invention is preferably 140 to 400, more preferably 160 or more, still more preferably 180 or more, particularly preferably 200 or more, and most preferably 210 or more. When the viscosity index of the lubricating oil composition is less than 140, it may be difficult to improve fuel economy while maintaining the HTHS viscosity at 150 ° C., and further, low temperature (for example, the viscosity grade of fuel economy oil) It may be difficult to reduce the viscosity at -35 ° C., which is the CCS viscosity measurement temperature defined in SAE viscosity grade 0W-X, which is known as Further, when the viscosity index of the lubricating oil composition exceeds 400, the evaporability may be deteriorated, and further, there may be a problem due to insufficient solubility of the additive and compatibility with the sealing material. is there.

The HTHS viscosity at 100 ° C. of the lubricating oil composition of the present invention is preferably 5.5 mPa · s or less, more preferably 5.0 mPa · s or less, still more preferably 4.9 mPa · s or less, particularly preferably. 4.8 mPa · s or less, most preferably 4.6 mPa · s or less. Further, it is preferably 3.5 mPa · s or more, more preferably 4.0 mPa · s or more, further preferably 4.4 mPa · s or more, and particularly preferably 4.5 mPa · s or more. In the present specification, the HTHS viscosity at 100 ° C. means a high temperature high shear viscosity at 100 ° C. as defined in ASTM D4683. When the HTHS viscosity at 100 ° C. is less than 3.5 mPa · s, there is a risk of insufficient lubricity, and when it exceeds 5.5 mPa · s, the necessary low temperature viscosity and sufficient fuel saving performance cannot be obtained. There is a fear.

The HTHS viscosity at 150 ° C. of the lubricating oil composition of the present invention is 2.7 mPa · s or less, preferably 2.65 mPa · s or less, particularly preferably 2.35 mPa · s or less. Further, it is preferably 1.95 mPa · s or more, more preferably 2.1 mPa · s or more, further preferably 2.2 mPa · s or more, and particularly preferably 2.25 mPa · s or more. In the present specification, the HTHS viscosity at 150 ° C. means a high temperature and high shear viscosity at 150 ° C. as defined in ASTM D4683. If the HTHS viscosity at 150 ° C. is less than 1.95 mPa · s, there is a risk of insufficient lubricity, and if it exceeds 2.7 mPa · s, sufficient fuel saving performance may not be obtained.

The ratio (X ₁₀₀ / X ₁₅₀ ) of the HTHS viscosity (X ₁₀₀ ) at ₁₀₀ ° C. to the HTHS viscosity (X ₁₅₀ ) at 150 ° C. of the lubricating oil composition of the present invention is preferably 2.0 or less. When the HTHS viscosity ratio X ₁₀₀ / X ₁₅₀ is 2.0 or less, high fuel efficiency can be realized while supporting the wear resistance. The lower limit of the ratio HTHS viscosity X ₁₀₀ / X ₁₅₀ is not particularly limited, but is preferably 1.8 or more. Since the ratio of the HTHS viscosity X ₁₀₀ / X ₁₅₀ is 1.8 or more, the base oil viscosity can be kept high, which is advantageous in terms of evaporability and wear resistance.

The evaporation loss amount of the lubricating oil composition according to the present invention is preferably 20% by mass or less, more preferably 15% by mass or less, and more preferably 14% by mass or less as the NOACK evaporation amount at 250 ° C. Is particularly preferred. When the NOACK evaporation amount of the lubricating base oil component exceeds 20% by mass, the evaporation loss of the lubricating oil is large, which causes an increase in viscosity and the like, which is not preferable. In this specification, the NOACK evaporation amount is a value obtained by measuring the evaporation amount of the lubricating oil measured according to ASTM D 5800. The lower limit of the NOACK evaporation amount at 250 ° C. of the lubricating oil composition is not particularly limited, but is usually 5% by mass or more.

The inventors of the present invention have examined a supercharger-equipped test engine under operating conditions where LSPI is likely to occur. As a result, differential scanning calorimetry (LSPI generation frequency in air or oxygen atmosphere at a pressure of 10 atm) DSC) was found to have a negative correlation with the self-ignition point.

In this engine test, in order to eliminate the influence of deposits generated in the combustion chamber, after performing precondition operation of partial load for 30 minutes at a rotational speed of 4000 rpm, throttle opening, rotational speed, injection timing, air-fuel ratio, etc. Were changed to operating conditions where LSPI is likely to occur (throttle fully open, rotation speed 1800 rpm). Thereafter, the number of LSPI generated in one hour was measured using a combustion pressure sensor mounted on each cylinder of the engine.

In DSC measurement, a 5 mg engine oil sample is heated with a reference material at a heating rate of 10 K / min in a 10 atm air or oxygen atmosphere, and the exothermic peak is a function of the difference in input energy and temperature obtained. Was measured as the auto-ignition point.

FIG. 1 shows the occurrence frequency of LSPI in an engine test as a self-ignition point (hereinafter referred to as “DSC (10 atm air atmosphere) self-ignition point) in DSC measurement of an engine oil sample used in the engine test under an air atmosphere at a pressure of 10 atm. Is a scatter plot plotted against. It can be seen that when the DSC (10 atm air atmosphere) self-ignition point rises from 260 ° C. to 270 ° C., for example, the frequency of occurrence of LSPI is reduced to about 1/7. The graph of FIG. 1 shows the correlation between the DSC (10 atm air atmosphere) self-ignition point and the frequency of LSPI generation. The auto-ignition point (hereinafter referred to as “DSC (10 atm) in DSC measurement under an oxygen atmosphere at a pressure of 10 atm is shown. It is considered that the correlation between the oxygen atmosphere) self-ignition point ") and the LSPI occurrence frequency is even higher.

The DSC (10 atm oxygen atmosphere) self-ignition point of the lubricating oil composition of the present invention is preferably 213 ° C. or higher, more preferably 215 ° C. or higher, further preferably 217 ° C. or higher, particularly preferably 220 ° C. or higher. The upper limit is not particularly limited, but is usually 300 ° C. or lower, and typically 280 ° C. or lower. When the DSC (10 atm oxygen atmosphere) self-ignition point is equal to or higher than the lower limit, the occurrence frequency of LSPI can be effectively suppressed.

In the lubricating oil composition of the present invention, the value of the parameter r _S represented by the following mathematical formula (1) is preferably 1.08 or more, more preferably 1.10 or more, and 1.15. More preferably, it is more preferably 1.20 or more. The parameter r _S is preferably 3.00 or less, more preferably 2.00 or less, and particularly preferably 1.50 or less.
r _S = ([S] + [Mo] + [Zn]) / ([Mg] + 2 × [Ca]) (1)
(In Formula (1), [S] represents the sulfur content derived from the additive (unit: mass ppm), [Mo] represents the molybdenum content (unit: mass ppm) in the lubricating oil composition, and [Zn]. ] Represents the zinc content (unit: mass ppm) in the lubricating oil composition, [Mg] represents the magnesium content (unit: mass ppm) in the lubricating oil composition, and [Ca] represents the lubricating oil composition. Represents the calcium content in the unit (unit: mass ppm).)
When the value of the parameter r _S is within the above range, it is possible to satisfy all the performances of fuel saving, engine cleanliness, and LSPI suppression with a good balance.

In the lubricating oil composition of the present invention, the value of the parameter r _S ′ represented by the following mathematical formula (2) is preferably 1.00 or more, more preferably 1.02 or more, It is more preferably 1.05 or more, particularly preferably 1.10 or more, and most preferably 1.15 or more. The parameter r _S ′ is preferably 2.50 or less, more preferably 2.00 or less, and particularly preferably 1.50 or less.
r _S ′ = ([S] ′ + [Mo] + [Zn]) / ([Mg] + 2 × [Ca]) (2)
(In Formula (2), [S] ′ represents a sulfur content (unit: mass ppm) derived from additives other than the sulfonate detergent, and [Mo] represents the molybdenum content (unit: in the lubricating oil composition). [Zn] represents the zinc content (unit: mass ppm) in the lubricating oil composition, [Mg] represents the magnesium content (unit: mass ppm) in the lubricating oil composition, [Ca] represents the calcium content (unit: mass ppm) in the lubricating oil composition.)
When the value of the parameter r _S ′ is within the above range, it is possible to satisfy all the performances of fuel saving, engine cleanliness, and LSPI suppression with a good balance.

<LSPI suppression method for internal combustion engine>
The LSPI suppression method for an internal combustion engine according to the second aspect of the present invention operates the internal combustion engine while lubricating the cylinder of the internal combustion engine using the lubricating oil composition according to the first aspect of the present invention described above. The process of carrying out. In the LSPI suppressing method of the present invention, the lubricating oil composition of the present invention may be used at least for lubricating a cylinder, and portions other than the cylinder of the internal combustion engine may be lubricated with the lubricating oil composition of the present invention together with the cylinder. In lubricating the cylinder of the internal combustion engine using the lubricating oil composition described above, a known lubricating oil supply mechanism can be employed without any particular limitation. By lubricating the cylinder of the internal combustion engine with the lubricating oil composition of the present invention, LSPI in the internal combustion engine is effectively suppressed.

Hereinafter, the present invention will be described in more detail based on examples and comparative examples. However, the present invention is not limited to these examples.

<Examples 1 to 8, Comparative Examples 1 to 5>
Lubricating oil compositions of the present invention (Examples 1 to 8) and comparative lubricating oil compositions (Comparative Examples 1 to 5) were prepared using the following base oils and additives, respectively. In the table, “inmass%” represents mass% based on the total amount of the base oil, “mass%” represents mass% based on the total amount of the composition, and “mass ppm” represents mass based on the total amount of the composition. Represents ppm.

(Base oil)
O-1: Group III base oil, kinematic viscosity (100 ° C.) 4.15 mm ² / s, aromatic content 0.2% by mass

(Metal-based detergent)
B1-1: CaCO ₃ overbased Ca salicylate, Ca content 8.0 mass%, metal ratio 3.0, base number (perchloric acid method) 225 mg KOH / g, sulfur content 0.0 mass%
B1-2: CaCO ₃ overbased Ca sulfonate, Ca content 12.75% by mass, base number (perchloric acid method) 325 mg KOH / g, sulfur content 2.0% by mass
B2-1: MgCO ₃ overbased Mg sulfonate, Mg content 9.3 mass%, base number (perchloric acid method) 400 mg KOH / g, sulfur content 2.0 mass%

(Molybdenum friction modifier)
C-1: sulfurized (oxy) molybdenum dithiocarbamate, alkyl group: combination of 8 and 13 carbon atoms, Mo content 10.0% by mass, sulfur content 10.8% by mass

(Antioxidant)
D-1: Amine-based antioxidant, nitrogen content 3.6% by mass
D-2: Phenolic antioxidant

(Zinc dithiophosphate)
E-1: Zinc dialkyldithiophosphate (alkyl group: secondary C6, Zn content 9.25% by mass, phosphorus content 8.5% by mass, sulfur content 17.6% by mass)

(Ashless dispersant)
G-1: polybutenyl succinimide, bistype, polybutenyl group number average molecular weight: 1300, nitrogen content: 1.75% by mass
G-2: Number average molecular weight of boric acid-modified polybutenyl succinimide, bistype, polybutenyl group: 1300, nitrogen content 1.5% by mass, boron content 0.78% by mass

(Viscosity index improver)
H-1: Polymethacrylate viscosity index improver, weight average molecular weight 500,000, PSSI: 5

(Other sulfur-containing additives)
I-1: alkyldithiothiadiazole, sulfur content 36.0% by mass
I-2: Sulfurized olefin, sulfur content 46.0% by mass

(Evaluation of lubricating oil composition)
For each of the lubricating oil compositions of Examples 1 to 6 and Comparative Examples 1 to 4, measurement of the deposit amount (HTT290 deposit) in the hot tube test and measurement of the friction coefficient (SRV friction coefficient) using an SRV friction tester went. The lubricating oil compositions of Examples 3 to 6 were further measured for HTHS viscosity at 100 ° C. and 150 ° C., kinematic viscosity at 100 ° C. and 40 ° C., and viscosity index. The results are shown in Tables 1-2. For the lubricating oil compositions of Examples 1, 7 to 8 and Comparative Examples 4 to 5, the DSC (10 atm oxygen atmosphere) self-ignition point was measured. The results are shown in Table 3. The measuring method is as follows.
(1) HTT 290 deposit: A hot tube test was conducted at 290 ° C. according to JPI-5S-55-99, and the weight (unit: mg) of the deposit adhered to the inner wall surface of the tube having a predetermined inner diameter and length was determined. It was measured. The less deposits, the higher the engine cleanliness.
(2) SRV friction coefficient: Using a SRV reciprocating friction and wear tester (manufactured by Optimol Instruments), a cylinder-on-disk test is performed at a temperature of 100 ° C., a load of 400 N, an amplitude of 1.5 mm, and a vibration frequency of 50 Hz, and the friction coefficient is measured. did.
(3) HTHS viscosity: measured in accordance with ASTM D-4683.
(4) Kinematic viscosity: Measured according to ASTM D-445.
(5) Viscosity index: measured in accordance with JIS K 2283-1993.
(6) DSC auto-ignition point: Using a differential pressure scanning calorimeter (manufactured by TA Instruments), perform differential scanning calorimetry at a pressure of 10 atm, an oxygen atmosphere, and a heating rate of 10 ° C./min. The ignition point was used. The higher the self-ignition point, the lower the LSPI occurrence frequency.

The lubricating oil composition of the present invention has an improved LSPI suppression capability, and at the same time, is excellent in engine cleanliness and fuel economy. Therefore, the lubricating oil composition of the present invention can be preferably used for lubrication of a supercharged gasoline engine, particularly a supercharged direct injection engine, in which LSPI tends to be a problem.

Claims

(A) a base oil having a kinematic viscosity at 100 ° C. of 2 to 8 mm 2 / s and an aromatic content of 10% by mass or less;
A metal detergent comprising (B) (B1) a metal detergent overbased with calcium carbonate and (B2) a metal detergent overbased with magnesium carbonate;
(C) containing sulfurized molybdenum dithiocarbamate or sulfurized oxymolybdenum dithiocarbamate,
Based on the total amount of the lubricating oil composition,
The calcium content is 1500 mass ppm or less,
Magnesium content is 300 mass ppm or more,
Molybdenum content is 600 mass ppm or more,
A lubricating oil composition for an internal combustion engine, having an HTHS viscosity at 150 ° C. of 2.7 mPa · s or less.
(D) containing an amine-based antioxidant and / or a phenol-based antioxidant,
The lubricating oil composition for an internal combustion engine according to claim 1.
(D) contains an amine antioxidant,
Based on the total amount of the lubricating oil composition,
The boron content is 0 mass ppm or more and less than 400 mass ppm,
The ratio (X 100 / X 150 ) of the HTHS viscosity (X 100 ) at 100 ° C. to the HTHS viscosity (X 150 ) at 150 ° C. is 2.0 or less.
The lubricating oil composition for an internal combustion engine according to claim 1 or 2.
Based on the total amount of the lubricating oil composition,
The boron content is 0 to 300 ppm by mass,
The calcium content is 1400-1500 ppm by mass,
The lubricating oil composition for an internal combustion engine according to claim 3.
Based on the total amount of the lubricating oil composition,
Magnesium content is 350-600 mass ppm,
The molybdenum content is 700 to 800 ppm by mass;
The lubricating oil composition for internal combustion engines according to claim 3 or 4.
(E) containing zinc dialkyldithiophosphate,
The sulfur content is 0.20 to 0.30 mass ppm based on the total amount of the lubricating oil composition;
The lubricating oil composition for an internal combustion engine according to any one of claims 3 to 5.
Of HTHS viscosity at 100 ℃ (X 100), the ratio of HTHS viscosity (X 0.99) at 150 ℃ (X 100 / X 150 ) is 1.8-2.0,
The lubricating oil composition for an internal combustion engine according to any one of claims 3 to 6.
An LSPI suppression method for an internal combustion engine, comprising a step of operating the internal combustion engine while lubricating a cylinder of the internal combustion engine using the lubricating oil composition according to any one of claims 1 to 7.