JP2015183152A - Lubricant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant composition for an internal combustion engine, enabling both of fuel economy and caulking reduction property of a turbocharger to be attained in an internal combustion engine with the turbocharger.SOLUTION: There is provided the lubricant composition containing in a base oil, (A) an over-basic phenate-based cleaner having a basic value of 100 mgKOH/g or more, (B) a sulfonate cleaner having the basic value of 150 mgKOH/g or less and (C) a dithiophosphoric acid zinc and satisfying following conditions (i) and (ii). [M]≥1100 (i) [M]+2×[P]≥2600 (ii), where [M] represents the metal content derived from (A) component and (B) component in the lubricant composition (mass.ppm) and [P] represents the phosphorus content derived from (C) component in the lubricant composition (mass.ppm).

Description

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

In recent years, various demands have been made on automobiles, such as miniaturization and high output of engines, fuel savings, compliance with exhaust gas regulations, etc. As a means to meet these demands, turbochargers, especially turbochargers. It has been increasingly mounted on the engine.
On the other hand, from the viewpoint of environmental problems in recent years, especially the reduction of carbon dioxide emissions, reducing the fuel consumption of automobiles is one of the important issues. For this reason, reducing the weight of automobiles, improving combustion, reducing engine friction, and driving Development and improvement of system equipment are being studied. For example, in order to reduce the friction of the engine, the improvement of the valve system structure such as the variable valve system mechanism, the reduction of the number of piston rings, the reduction of the surface roughness of the sliding member, the improvement of the material surface, the lean combustion engine and Development of direct fuel injection engines, installation of turbochargers, and application of fuel-saving engine oil are underway.

Although it is possible to increase the output efficiently by installing a turbocharger, on the other hand, the turbocharger is exposed to high temperature residual heat, which causes oil deterioration, especially the generation of deposits due to oil coking in the turbocharger Danger arises. In particular, when the engine is suddenly stopped after operating a turbocharged engine at high speed and high load, that is, at the time of heat soak back of the turbocharger, the turbine side wall temperature becomes 300 ° C or higher. Caulking is likely to occur. As a result, the oil flow path is blocked, the floating metal is seized, the caulking deposit enters the space between the floating metal and the shaft, and the floating metal moves abnormally, and the floating metal is worn away. Problems such as compressor blades coming into contact with the casing and being damaged.
Therefore, an engine oil used for a turbocharged engine is required to have excellent thermal and oxidation stability and is difficult to coking even at a high temperature of 300 ° C. or higher.

  As an engine oil capable of greatly suppressing coking, for example, Patent Document 1 discloses a multigrade engine oil in which a specific high-viscosity base oil such as a base oil having a kinematic viscosity of 16 to 45 cSt at 100 ° C. is blended. . However, coking is remarkable when a specific high-viscosity base oil is not blended, and it has been extremely difficult to suppress this. Further, as a lubricating oil suitable for an engine equipped with a turbocharger, in Patent Document 2, at least one base oil selected from organic acid esters and alkyldiphenyl ethers, a phosphorus-based antiwear agent, and a benzotriazole or benzotriazole derivative are used. Has disclosed a lubricating oil composition excellent in wear resistance. However, coking suppression has not been studied. In Patent Document 3, a specific thiophosphate or metal salt of a phosphate ester, a metal salt or amine salt of a specific dithiophosphate, a metal-based detergent, an ashless dispersant, an antioxidant, etc. The added lubricating oil composition for internal combustion engines is described which has excellent base number maintenance and high temperature cleanliness. However, this document also does not disclose or suggest the coking prevention properties of the turbocharged engine.

In order to improve the fuel economy of engine oil, it is necessary to reduce the viscosity of the base oil to reduce the viscous resistance and to add a friction reducing agent such as molybdenum dithiocarbamate (MoDTC) to reduce the friction under boundary lubrication. Valid. Of the friction reducing agents, MoDTC is the most effective additive, and it is known that engine oil blended with MoDTC has high fuel efficiency.
However, it has been reported that when MoDTC is blended at a high concentration, the amount of deposit at a high temperature is remarkably increased (Non-patent Document 1). Therefore, it has been impossible to achieve both fuel efficiency and turbo coking performance by using MoDTC as a lubricating oil composition for a turbocharged engine.

JP 59-122595 A JP-A-8-259980 JP 2002-294271 A

Automobile Engineering Society 2008 Academic Lecture Preprint 153-30085146

  An object of the present invention is to provide a lubricating oil composition that can achieve both fuel saving and coking reduction in a turbocharger in an internal combustion engine equipped with a turbocharger.

  As a result of intensive studies on the above problems, the present inventors have completed the present invention.

That is, the present invention provides (A) an overbased phenate detergent having a base number of 100 mgKOH / g or more, (B) a sulfonate detergent having a base number of 150 mgKOH / g or less, and (C) zinc dithiophosphate. And a lubricating oil composition used for an internal combustion engine equipped with a turbocharger characterized by satisfying the following conditions (i) and (ii).
[M] ≧ 1100 (i)
[M] + 2 × [P] ≧ 2600 (ii)
(Wherein [M] represents the amount of metal (mass ppm) derived from the component (A) and the component (B) in the lubricating oil composition, and [P] represents the amount of phosphorus derived from the component (C) in the lubricating oil composition. (Mass ppm)

  The lubricating oil composition of the present invention can achieve both high fuel efficiency and effective coking suppression in an internal combustion engine equipped with a turbocharger that is often exposed to high temperatures.

  Hereinafter, the present invention will be described in detail.

  The base oil according to the lubricating oil composition of the present invention is not particularly limited and those usually used can be used. For example, mineral oil or synthetic oil is mentioned.

  As mineral oil, for example, a lubricating oil fraction obtained by distillation under reduced pressure of atmospheric residual oil obtained by atmospheric distillation of crude oil can be removed by solvent, solvent extraction, hydrocracking, solvent dewaxing, hydrogenation Examples include mineral base oils that have been refined by performing one or more treatments such as refining, or mineral oil base oils produced by isomerizing wax isomerized mineral oil, GTLWAX (gas-tree liquid wax) produced by the Fischer-Tropsch process, etc. It is done.

  Synthetic oils include, for example, poly α-olefins (ethylene-propylene copolymer, polybutene, 1-octene oligomer, 1-decene oligomer, and hydrides thereof), alkylbenzene, alkylnaphthalene, monoester (butyl stearate). Octyl laurate), diester (ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sepacate, etc.), polyester (trimellitic acid ester, etc.), polyol ester (tri Methylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate), polyoxyalkylene glycol Obtained from synthetic waxes such as polyphenyl ether, dialkyl diphenyl ether, phosphate esters (tricresyl phosphate, etc.), fluorine-containing compounds (perfluoropolyether, fluorinated polyolefins, etc.), silicone oil, FT reaction and / or petroleum refining process High-performance hydrocarbon base oil obtained by isomerization and hydrogenation of the resulting wax (preferably slack wax obtained in the solvent dewaxing step), and obtained by hydrogenating naturally-occurring unsaturated hydrocarbons such as terpenes Examples include hydrocarbon base oils.

  As a base oil of the lubricating oil composition of the present invention, the above base oils may be used alone or in combination of two or more.

The kinematic viscosity at 100 ° C. of the base oil is not particularly limited, but is preferably 8.5 mm ² / s or more, and more preferably 9.0 mm ² / s or more. On the other hand, it is preferably 20.0 mm ² / s or less, more preferably 15.0 mm ² / s, more preferably less 12.0 mm ² / s.
When the kinematic viscosity at 100 ° C. of the base oil is less than 8.5 mm ² / s, the oil film is not sufficiently formed at the lubrication site, so that the lubricity is poor and the evaporation loss of the base oil may increase. On the other hand, when the kinematic viscosity exceeds 20.0 mm ² / s, fuel economy and coking reduction in a turbocharger deteriorate.
The kinematic viscosity at 100 ° C. in the present invention means the kinematic viscosity at 100 ° C. defined in JIS K2283.

The viscosity index of the base oil is not particularly limited, but is preferably 90 or more, more preferably 100 or more, and further preferably 120 or more. In particular, it is preferable to use those having a viscosity index of about 135 to 180 such as normal paraffin, slack wax, GTL wax, etc., or isoparaffin mineral oil obtained by isomerizing these. When the viscosity index is less than 90, fuel economy and coking reduction in the turbocharger may be deteriorated.
In addition, the viscosity index as used in the field of this invention means the viscosity index prescribed | regulated to JISK2283.

The total aromatic content of the base oil is not particularly limited, but is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.3% by mass or less. When the total aromatic content is more than 1.0% by mass, the oxidation stability is poor. On the other hand, the total aromatic content may be 0% by mass, but is preferably 0.05% by mass or more from the viewpoint of the solubility of the additive.
In addition, the total aromatic content as used in the field of this invention means the content of aromatic fraction measured based on ASTM D2549.

Although there is no restriction | limiting in particular in the sulfur content of a base oil, 1.0 mass% or less is preferable, 0.5 mass% or less is more preferable, 0.2 mass% or less is further more preferable.
In addition, the sulfur content as used in the field of this invention means the sulfur content measured based on JISK2541-1996.

  The lubricating oil composition of the present invention contains an overbased phenate detergent having a base number of 100 mgKOH / g or more as the component (A).

Examples of the overbased phenate detergent include an alkali metal salt of an alkylphenol sulfide or an overbased salt of an alkaline earth metal salt.
Carbon number of an alkyl group is 8-30 normally, Preferably it is 12-20. If the carbon number is shorter than 8, the solubility in the base oil may be inferior. If the carbon number is longer than 30, the production is difficult and the heat resistance may be inferior.

  Examples of the alkali metal or alkaline earth metal include sodium, potassium, magnesium, barium, and calcium. Magnesium or calcium is preferable, and calcium is particularly preferable.

The base number of the component (A) is 100 mgKOH / g or more, preferably 150 mgKOH / g or more, and more preferably 250 mgKOH / g or more. On the other hand, 450 mgKOH / g or less is preferable, and 350 mgKOH / g or less is more preferable. When the base number is less than 100 mgKOH / g, the turbo coking performance may be deteriorated, and when it exceeds 450 mgKOH / g, there may be a problem in solubility.
In addition, the base number as used in the field of this invention is 7 of JIS K2501 "Petroleum products and lubricating oil-neutralization number test method". Means the base number measured by the perchloric acid method according to the above.

The metal ratio of the component (A) is not particularly limited, but is preferably 1 or more, more preferably 2 or more, further preferably 2.5 or more, on the other hand, 20 or less, more preferably 15 or less, and 10 or less. Further preferred.
In the present invention, the metal ratio is represented by the valence of the metal element × the content of the metal element (mol%) / the content of the soap group (mol%). The metal element refers to a soap group such as calcium and magnesium. Means a sulfonic acid group, a phenol group, a salicylic acid group, and the like.

Although there is no restriction | limiting in particular in content of (A) component, It is preferable that it is 500 mass ppm or more in conversion of a metal whole quantity basis and a metal amount, 1000 mass ppm or more is more preferable, 2000 mass ppm or more is further more preferable. . On the other hand, 10000 mass ppm or less is preferable, 5000 mass ppm or less is more preferable, and 4000 mass ppm or less is more preferable.
If the content is less than 500 ppm by mass, the required cleanliness and acid neutralization may not be obtained, and if it exceeds 10000 ppm by mass, an excess metal component may be deposited.

  The lubricating oil composition of the present invention contains a sulfonate detergent having a base number of 150 mgKOH / g or less as the component (B).

  Examples of the sulfonate detergent include alkali metal salts or alkaline earth metal salts of alkyl aromatic sulfonic acids obtained by sulfonating alkyl aromatic compounds having a weight average molecular weight of 300 to 1500, preferably 400 to 700. Can be used.

Examples of the alkyl aromatic sulfonic acid include so-called petroleum sulfonic acid and synthetic sulfonic acid. Examples of petroleum sulfonic acids include those obtained by sulfonating alkyl aromatic compounds of a lubricating oil fraction of mineral oil, and so-called mahoganic acid that is by-produced during white oil production. Examples of synthetic sulfonic acids include sulfonation of alkylbenzenes having linear or branched alkyl groups, which are produced as a by-product from an alkylbenzene production plant that is a raw material for detergents or obtained by alkylating polyolefins to benzene. Or sulfonated alkylnaphthalene such as dinonylnaphthalene.
The sulfonating agent for sulfonating these alkyl aromatic compounds is not particularly limited, but usually fuming sulfuric acid or sulfuric anhydride is used.

  Examples of the alkali metal or alkaline earth metal include sodium, potassium, magnesium, barium, and calcium. Magnesium or calcium is preferable, and calcium is particularly preferable.

  The base number of component (B) is 150 mgKOH / g or less, preferably a neutral sulfonate less than 50 mgKOH / g, more preferably 40 mgKOH / g or less, and even more preferably 30 mgKOH / g or less. When the base number exceeds 150 mgKOH / g, the cleansing and dispersing action by the soap group component cannot be sufficiently obtained.

  The metal ratio of component (B) is preferably 1 or more. Moreover, 10 or less is preferable, 5 or less is more preferable, and 2 or less is further more preferable.

The content of the component (B) is not particularly limited, but is preferably 30 mass ppm or more, more preferably 50 mass ppm or more, even more preferably 100 mass ppm or more, and 150 mass in terms of the total amount of the composition and in terms of metal amount. ppm or more is particularly preferable. On the other hand, 1000 mass ppm or less is preferable, 800 mass ppm or less is more preferable, and 500 mass ppm or less is more preferable.
If the content is less than 30 ppm by mass, the required cleanliness and acid neutralization may not be obtained, and if it exceeds 1000 ppm by mass, the viscosity characteristics will deteriorate and the fuel efficiency will deteriorate.

  The lubricating oil composition of the present invention contains zinc dithiophosphate as the component (C). Examples of zinc dithiophosphate include compounds represented by the following general formula (1).

[Wherein R ¹ , R ² , R ³ and R ⁴ may be the same or different and each represents a hydrocarbon group having 1 or more carbon atoms. ]

Examples of the hydrocarbon group represented by R ^{1 to} R ⁴ include an alkyl group having 1 to 24 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, an alkylcycloalkyl group having 6 to 11 carbon atoms, and 2 carbon atoms. -24 alkenyl group, C6-C18 aryl group, C7-C24 alkylaryl group, and C7-C12 arylalkyl group can be mentioned.

Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, a hexyl group, a heptyl group, a 3-heptyl group, and an octyl group. Group, 2-ethylhexyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, 2-ethylbutyl group, 1-methylphenyl group, 1, 3-dimethylbutyl group, 1,1,3,3-tetramethylbutyl group, 1-methylhexyl group, isoheptyl group, 1-methylheptyl group, 1,1,3-trimethylhexyl group and 1-methylundecyl group Etc.
Among these, a C3-C12 alkyl group is preferable and a C4-C8 alkyl group is more preferable.

Examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and a cyclododecyl group.
Examples of the cycloalkylalkyl group include a cyclopentylmethyl group and a cyclohexylmethyl group.

Examples of the aryl group include a phenyl group, a tolyl group, and a xylyl group.
Examples of the alkylaryl group include ethylphenyl group, vinylphenyl group, methylphenyl group, dimethylphenyl group, trimethylphenyl group, ethylphenyl group, isopropylphenyl group, tert-butylphenyl group, di-tert-butylphenyl group, 2, Examples include 6-di-tert-butyl-4-methylphenyl group.
Examples of the arylalkyl group include a benzyl group, a phenylethyl group, a phenylpropyl group, a phenylbutyl group, a phenylpentyl group, a phenylhexyl group, and a naphthylethyl group.

Among these, an alkyl group is preferable, and a primary alkyl group is particularly preferable. The primary alkyl group means that the carbon bonded to oxygen among the carbons of R ^{1 to} R ⁴ is a primary carbon. That is, the alkyl group is preferably a group represented by —CH ₂ —R ′ (R ′ is a hydrogen atom or a linear or branched alkyl group).

  (C) As the zinc dithiophosphate, zinc dialkyldithiophosphate is particularly preferable. Specifically, zinc di-pri-propyl dithiophosphate, zinc di-sec-propyl dithiophosphate, zinc di-pri-butyldithiophosphate, di- zinc sec-butyldithiophosphate, zinc di-pri-pentyldithiophosphate, zinc di-sec-pentyldithiophosphate, zinc di-pri-hexyldithiophosphate, zinc di-sec-hexyldithiophosphate, di-pri-octyldithiophosphate Zinc, zinc di-sec-octyl dithiophosphate and the like can be mentioned.

Although there is no restriction | limiting in particular in content of (C) component, It is preferable that it is 300 mass ppm or more in conversion of the total amount of composition and phosphorus amount, 500 mass ppm or more is more preferable, 800 mass ppm or more is further more preferable. . On the other hand, 2000 mass ppm or less is preferable, 1500 mass ppm or less is more preferable, and 1200 mass ppm or less is more preferable.
When the content is less than 300 ppm by mass, sufficient wear resistance may not be obtained, and when it exceeds 2000 ppm by mass, the exhaust gas treatment catalyst may be adversely affected.

The lubricating oil composition of the present invention must satisfy the following conditions (i) and (ii).
[M] ≧ 1100 (i)
[M] + 2 × [P] ≧ 2600 (ii)

[M] in the formula represents the amount of metal (mass ppm) derived from the component (A) and the component (B) on the basis of the total amount of the composition of the lubricating oil composition.
[P] in the formula represents the amount of phosphorus (mass ppm) derived from the component (C) on the basis of the total amount of the composition of the lubricating oil composition.

  [M] is 1100 or more, preferably 1500 or more, more preferably 2000 or more, and still more preferably 3000 or more. By setting [M] to 1100 or more, coking resistance to the turbocharger can be improved. On the other hand, it is preferably 10,000 or less, more preferably 5000 or less, and still more preferably 4000 or less. Exceeding 10,000 is not preferable because an excessive metal component may be deposited.

  [M] + 2 × [P] is 2600 or more, preferably 3000 or more, and more preferably 4000 or more. By setting [M] + 2 × [P] to 2600 or more, the coking resistance against the turbocharger can be improved. On the other hand, 10,000 or less is preferable and 7000 or less is more preferable. If it exceeds 10,000, the exhaust gas treatment catalyst may be adversely affected.

The lubricating oil composition of the present invention may further contain an ashless dispersant as component (D).
The ashless dispersant is not particularly limited and those commonly used can be used. Examples thereof include nitrogen-containing compounds or derivatives having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule.
One of these compounds may be used alone, or a mixture of two or more compounds in an arbitrary mixing ratio may be used.

  The alkyl group or alkenyl group may be linear or branched, but is preferably branched from an olefin oligomer such as propylene, 1-butene, isobutylene, or a co-oligomer of ethylene and propylene. Examples thereof include an alkyl group and a branched alkenyl group.

  Carbon number of an alkyl group or an alkenyl group is 40-400 normally, Preferably it is 60-350. If it is less than 40, the solubility in the base oil may be reduced, whereas if the carbon number exceeds 400, the low-temperature fluidity of the lubricating oil composition may be deteriorated.

As the component (D), more specifically,
(D1) Succinimide having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or a derivative thereof (D2) At least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule Exemplified benzylamine or derivative thereof (D3) Polyamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or one or more compounds selected from derivatives thereof it can.
In the present invention, (D1) is preferable from the viewpoint of dispersion performance.

  More specifically, examples of (D1) succinimide include compounds represented by the following general formula (2) or (3).

In the general formulas (2) and (3), R ⁵ , R ⁶ and R ⁷ each independently represent an alkyl group or alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350 carbon atoms, and b is 1 -5, preferably 2-4, c is 0-4, preferably 1-3.

  Although the production method of this succinimide is not limited at all, for example, after reacting polyolefin such as propylene oligomer, polybutene, ethylene-propylene copolymer and the like with maleic anhydride to obtain alkenyl succinic anhydride, diethylenetriamine , Imidized with polyamines such as triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and the like.

  In addition, in the imidization, succinimide is added to one end of polyamine with succinic anhydride as shown in general formula (2), and succinic anhydride is added to both ends of polyamine. In addition, there is a so-called bis-type succinimide represented by the general formula (3). As the component (D1), any of them or a mixture thereof can be used, but a bis-type succinimide represented by the formula (3) is preferable from the viewpoint of high temperature cleanliness.

  (D2) More specifically, examples of benzylamine include compounds represented by the following general formula (4).

In the general formula (4), R ⁸ represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350, and d represents a number of 1 to 5, preferably 2 to 4, respectively. Yes.

  The method for producing this benzylamine is not limited in any way. For example, after reacting polyolefin such as propylene oligomer, polybutene, ethylene-propylene copolymer with phenol to form alkylphenol, formaldehyde, diethylenetriamine and triethylene are added thereto. It can be obtained by reacting polyamines such as tetramine, tetraethylenepentamine, pentaethylenehexamine and the like by Mannich reaction.

  More specifically, examples of (D3) polyamine include compounds represented by the following general formula (5).

In the general formula (5), R ⁹ represents an alkyl group or an alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350, and e represents a number of 1 to 5, preferably 2 to 4, respectively. Yes.

The production method of this polyamine is not limited at all. For example, after chlorinating a polyolefin such as propylene oligomer, polybutene, or ethylene-propylene copolymer, ammonia, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylene is added thereto. It can be obtained by reacting a polyamine such as pentamine or pentaethylenehexamine.

  As the component (D), derivatives of these nitrogen-containing compounds are also preferably used. Specific examples of the derivative of component (D) include, for example, monocarboxylic acids having 2 to 30 carbon atoms (fatty acids, etc.), oxalic acid, phthalic acid, trimellitic acid, pyromellitic acid, etc. A so-called acid-modified compound obtained by allowing a polycarboxylic acid having 2 to 30 carbon atoms to act to neutralize or amidate part or all of the remaining amino group and / or imino group; boric acid to these nitrogen-containing compounds So-called boron-modified compounds obtained by neutralizing some or all of the remaining amino groups and / or imino groups; so-called sulfur-modified compounds obtained by reacting these nitrogen-containing compounds with sulfur compounds; and these nitrogen-containing compounds Examples of the compound include modified compounds in which two or more kinds of modifications selected from acid modification, boron modification, and sulfur modification are combined.

  The ashless dispersant may not be contained, but when it is contained, its content is usually 0.1 to 5% by mass, preferably 0.5 to 4.5% by mass, more preferably based on the total amount of the composition. 1 to 4% by mass. When the content is less than 0.1% by mass, the turbo coking performance may be deteriorated. When the content exceeds 5% by mass, not only an effect commensurate with the content cannot be obtained, but also the cleanliness deteriorates. Tend to.

  In addition to these, any additive generally used in lubricating oils can be further added to the lubricating oil composition of the present invention. Examples of such additives include extreme pressure agents, antioxidants, friction modifiers, viscosity index improvers, corrosion inhibitors, rust inhibitors, demulsifiers, metal deactivators, antifoaming agents, or coloring. An agent can be mentioned.

Examples of extreme pressure agents include phosphites, thiophosphites, dithiophosphites, trithiophosphites, phosphate esters, thiophosphates, dithiophosphates ( (Excluding component (C)), trithiophosphates, amine salts thereof, metal salts thereof, derivatives thereof, dithiocarbamates, disulfides, polysulfides, sulfurized olefins, and sulfurized fats and oils.
The content of the extreme pressure agent is usually 0.01 to 5% by mass based on the total amount of the composition.

Examples of the antioxidant include ashless antioxidants such as phenols and amines, and metal antioxidants. Of these, phenolic antioxidants are preferred because of their excellent anti-coking properties, and phenolic antioxidants having bisphenol or ester bonds are preferred. Specifically, 3 such as octyl-3- (3,5-ditertiarybutyl-4-hydroxyphenyl) propionate and octyl-3- (3-methyl-5-tertiarybutyl-4-hydroxyphenyl) propionate , 5-dialkyl-4-hydroxyphenyl substituted fatty acid esters (one alkyl group is a tertiary butyl group and the rest are a methyl group or a tertiary butyl group) are particularly preferred.
The content of the antioxidant is usually 0.1 to 5% by mass, preferably 0.5 to 2% by mass, based on the total amount of the composition.

Examples of the friction modifier include organic molybdenum compounds, fatty acid esters, aliphatic amines, fatty acid amides, and the like.
Content of a friction modifier is 0.01-5 mass% normally on the composition whole quantity basis.

Examples of the viscosity index improver include, for example, a polymethacrylate viscosity index improver, an olefin copolymer viscosity index improver, a styrene-diene copolymer viscosity index improver, and a styrene-maleic anhydride copolymer viscosity index improver. Or a polyalkyl styrene type viscosity index improver is mentioned. Among these, an olefin copolymer viscosity index improver or a styrene-diene copolymer viscosity index improver is preferable because it is superior in anti-coking property, and an ethylene-α-olefin copolymer viscosity index improver is particularly preferable. preferable. The weight average molecular weight of these viscosity index improvers is usually 800 to 1,000,000, preferably 100,000 to 900,000.
The content of the viscosity index improver is usually 0.1 to 20% by mass based on the total amount of the composition.

Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, and imidazole compounds.
Examples of the rust inhibitor include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, and polyhydric alcohol ester.
Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthyl ether.
Content of a corrosion inhibitor, a rust inhibitor, and a demulsifier is 0.005-5 mass% normally on the composition whole quantity basis.

Examples of metal deactivators include imidazoline, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bis. Dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, or β- (o-carboxybenzylthio) propiononitrile.
Content of a metal deactivator is 0.005-1 mass% normally on the composition whole quantity basis.

Examples of antifoaming agents include silicone oils, alkenyl succinic acid derivatives, esters of polyhydroxy aliphatic alcohols and long chain fatty acids, methyl salicylate, o-hydroxybenzyl alcohol, aluminum stearate, potassium oleate, N-dialkyl-allylamine Nitroaminoalkanol, aromatic amine salt of isoamyl octyl phosphate, alkylalkylene diphosphate, metal derivative of thioether, metal derivative of disulfide, fluorine compound of aliphatic hydrocarbon, triethylsilane, dichlorosilane, alkylphenyl polyethylene glycol ether sulfide, fluoro An alkyl ether is mentioned.
The content of the antifoaming agent is usually 0.0005 to 1% by mass based on the total amount of the composition.

The kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is usually 5.5 to 21.9 mm ² / s, preferably 9.3 to 16.3 mm ² / s.

  The lubricating oil composition of the present invention exhibits high fuel economy and coking prevention. Therefore, it can be suitably used as a lubricating oil composition for an internal combustion engine equipped with a turbocharger that is often exposed to high temperatures, and coking can be effectively suppressed in the internal combustion engine.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(Examples 1-8, Comparative Examples 1-6)
Lubricating oil compositions having the compositions shown in Table 1 were prepared. The ratio (volume%) of the base oil is based on the total amount of the base oil, and the added amount (mass%) of each additive is based on the total amount of the composition. The coking prevention property of each lubricating oil composition was evaluated by the following panel coking test.

(Panel coking test)
Put 300 mL of the lubricating oil composition in a test container equipped with a splasher, and attach an aluminum panel. The sample oil and the panel are heated until the oil temperature reaches 100 ° C and the panel temperature reaches 320 ° C. When the condition temperature is reached, the splasher is rotated at 1000 rpm to splash oil on the panel. Splashing takes place in a cycle of 15 seconds and then 45 seconds. After 3 hours, the weight (mg) of carbon or the like attached to the aluminum panel is measured.

Claims (5)

The base oil contains (A) an overbased phenate detergent having a base number of 100 mgKOH / g or more, (B) a sulfonate detergent having a base number of 150 mgKOH / g or less, and (C) zinc dithiophosphate. A lubricating oil composition for use in an internal combustion engine equipped with a turbocharger characterized by satisfying the following conditions (i) and (ii):
[M] ≧ 1100 (i)
[M] + 2 × [P] ≧ 2600 (ii)
(Wherein [M] represents the amount of metal (mass ppm) derived from the component (A) and the component (B) in the lubricating oil composition, and [P] represents the amount of phosphorus derived from the component (C) in the lubricating oil composition. (Mass ppm)   The lubricating oil composition according to claim 1, wherein the sulfonate detergent as component (B) is a neutral sulfonate detergent with a base number of less than 50 mgKOH / g.   The lubricating oil composition according to claim 1 or 2, wherein the phenate detergent is calcium phenate and the sulfonate detergent is calcium sulfonate. The lubricating oil composition according to claim 1, the kinematic viscosity at 100 ° C. of the base oil is equal to or less than 8.5 mm ² / s or more 20.0 mm ² / s. Furthermore, (D) Ashless dispersing agent is contained 0.1 mass% or more and 5 mass% or less, The lubricating oil composition in any one of Claims 1-4 characterized by the above-mentioned.