WO2022250018A1

WO2022250018A1 - Lubricant composition for internal combustion engine

Info

Publication number: WO2022250018A1
Application number: PCT/JP2022/021115
Authority: WO
Inventors: 朱村本; 秀雄常岡
Original assignee: Ｅｎｅｏｓ株式会社
Priority date: 2021-05-25
Filing date: 2022-05-23
Publication date: 2022-12-01
Also published as: CN117242160A; JP2022180774A

Abstract

Provided is a lubricant composition for an internal combustion engine, comprising: (A) a lubricant base oil which contains one or more mineral-oil-based base oils and which has a kinematic viscosity of 2.5-4.0 mm2/s at 100°C; and (B) magnesium salicylate the content of which is 0.1-10 mass% based on the total amount of the composition, wherein the HTHS viscosity is 1.6-2.5 mPa·s at 150°C.<sp /> This lubricant composition for an internal combustion engine exhibits both good fuel saving performance and an LSPI-reducing effect.

Description

Lubricating oil composition for internal combustion engine

The present invention relates to a lubricating oil composition for internal combustion engines. The present invention relates in particular to internal combustion engine lubricating oil compositions for passenger cars.

In recent years, there have been various demands for internal combustion engines for automobiles, such as smaller size, higher output, fuel efficiency, and compliance with exhaust gas regulations. In particular, for the purpose of improving the fuel efficiency of internal combustion engines for automobiles, downsizing turbo engines are in progress.

Downsizing turbo engines have a higher compression ratio than normal engines, and the problem is the increase in the frequency of abnormal combustion (LSPI: Low Speed Pre-Ignition) at low engine speeds (non-patent Reference 1). The occurrence of LSPI is believed to be affected by calcium-based detergents in lubricating oil for internal combustion engines. For this reason, in order to maintain the detergency and neutralization of internal combustion engine lubricating oil, some of the metallic detergents have been replaced with magnesium detergents to develop lubricating oils for internal combustion engines (patent References 1 and 2).

Japanese Patent Application Laid-Open No. 2017-105886 Japanese Unexamined Patent Publication No. 2016-196667

On the other hand, even if magnesium-based detergents among metal-based detergents increase, there is a demand for further improvement in fuel efficiency. With the lubricating oils for internal combustion engines described in Patent Documents 1 and 2, there were cases where good fuel economy performance and LSPI reduction effects could not be obtained.

The present inventors have diligently studied a lubricating oil composition for internal combustion engines that has both fuel-saving performance and an LSPI reduction effect. As a result of studies, the present inventors have found that by combining a specific HTHS viscosity at 150°C in lubricating oil for internal combustion engines and magnesium salicylate as a metallic detergent, both the effect of reducing LSPI and the further improvement of fuel efficiency can be achieved. I found what I can do. That is, the present inventors have found that the above problems can be solved by adopting the following configuration, and have completed the invention.

The present invention has been made based on such findings, and is as follows.
<1>
(A) a lubricating base oil having a kinematic viscosity at 100° C. of 2.5 mm ² /s or more and 4.0 mm ² /s or less, which contains one or more mineral base oils, and (B) based on the total amount of the composition A lubricating oil composition for an internal combustion engine containing 0.1% by mass or more and 10% by mass or less of magnesium salicylate,
The lubricating oil composition for an internal combustion engine, which has an HTHS viscosity of 1.6 mPa·s or more and 2.5 mPa·s or less at 150°C.
<2>
(B) the content of magnesium salicylate is 0.1% by mass or more and 3.0% by mass or less based on the total amount of the composition; and (C) the content of the viscosity index improver is 0.00% based on the total amount of the composition. The lubricating oil composition for internal combustion engines according to <1>, which is 1% by mass or more and 10% by mass or less.
<3>
The lubricating oil composition for an internal combustion engine according to <1> or <2>, further comprising (D) a molybdenum-based friction modifier as a friction modifier in an amount of 0.01% by mass or more and 10% by mass or less based on the total amount of the composition.
<4>
The lubricating oil composition for internal combustion engines according to any one of <1> to <3>, wherein the magnesium salicylate has a base number of 350 mgKOH/g or less.
<5>
The lubricating oil composition for an internal combustion engine according to any one of <1> to <4>, which has an HTHS viscosity at 150°C of 1.6 mPa·s or more and 2.0 mPa·s or less.
<6>
The lubricating oil composition for internal combustion engines according to any one of <1> to <5>, wherein the LSPI frequency index calculated by the following formula (6) is 0 or less.
Equation (6): LSPI frequency index = 6.59 x Ca-26.6 x P-5.12 x Mo + 1.69
(In formula (6), Ca represents the calcium content (mass%) in the composition, P represents the phosphorus content (mass%) in the composition, and Mo represents the molybdenum content (mass%) in the composition. %).).

According to the lubricating oil composition for internal combustion engines of the present invention, it is possible to provide a lubricating oil composition for internal combustion engines that has both good fuel economy performance and an LSPI reduction effect.

[A] Lubricating base oil In the lubricating oil composition of the present invention, a mineral base oil can be used as the lubricating base oil.

The mineral base oil used in the lubricating oil composition of the present invention includes distillate oil obtained by atmospheric distillation of crude oil. Alternatively, a lubricating oil fraction obtained by further refining the distillate obtained by vacuum distillation of this distillate by various refining processes can also be used. As the refining process, hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, clay treatment, and the like can be appropriately combined. A lubricating base oil that can be used in the present invention can be obtained by combining these refining processes in an appropriate order. Mixtures of refined oils with different properties obtained by subjecting different crude oils or distillates to different combinations of refining processes can also be used.

As the mineral base oil used in the lubricating oil composition of the present invention, it is preferable to use one belonging to Group III base oil in the API classification. API Group III base oils are mineral base oils having a sulfur content of 0.03 wt.% or less, a saturates content of 90 wt.% or more, and a viscosity index of 120 or more. Multiple types of Group III base oils may be used, or only one type may be used.

The lubricating oil composition of the present invention may contain only a mineral base oil as the lubricating base oil, or may contain other lubricating base oils. Specifically, in the lubricating oil composition of the present invention, the content of the mineral base oil is based on the lubricating base oil, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass Above, it can be 90% by mass or more, 95% by mass or more, or 99% by mass or more.
As other lubricating base oils, for example, synthetic base oils can be used. Synthetic base oils include, for example, polyolefins such as poly-α-olefins, polyesters, polyalkylene glycols, alkylbenzenes, alkylnaphthalenes, and GTL base oils.

The kinematic viscosity at 100° C. of the lubricating base oil contained in the lubricating oil composition of the present invention is 2.5 mm ² /s or more and 4.0 mm ² /s or less. The kinematic viscosity at 100° C. of the lubricating base oil of the present invention is preferably 3.0 mm ² /s or higher, more preferably 3.2 mm ² /s or higher, still more preferably 3.4 mm ² /s or higher. Also, the upper limit is preferably 3.9 mm ² /s or less, more preferably 3.8 mm ² /s or less, and even more preferably 3.6 mm ² /s or less. A specific range is 2.5 mm ² /s or more and 4.0 mm ² /s or less, preferably 3.0 mm ² /s or more and 3.9 mm ² /s or less, more preferably 3.2 mm ² /s or more. 0.8 mm ² /s or less, more preferably 3.4 mm ² /s or more and 3.6 mm ² /s or less. When the kinematic viscosity at 100° C. of the lubricating base oil is 4.0 mm ² /s or less, sufficient fuel saving performance can be obtained. In addition, since the kinematic viscosity at 100° C. of the lubricating base oil is 2.5 mm ² /s or more, it is possible to ensure the formation of an oil film at the lubricating points and to reduce the evaporation loss of the lubricating oil composition.
The above kinematic viscosity at 100° C. means the kinematic viscosity in a state in which all the lubricating base oils are mixed, that is, the kinematic viscosity of the base oil as a whole. That is, it does not mean the kinematic viscosity of a specific lubricating base oil when a plurality of base oils are included.
As used herein, "kinematic viscosity at 100°C" means kinematic viscosity at 100°C measured according to ASTM D-445.

In the lubricating oil composition of the present invention, the content of the lubricating base oil is based on the total amount of the lubricating oil composition, for example, 50% by mass or more and 95% by mass or less, preferably 60% by mass or more and 95% by mass or less, more preferably is 70% by mass or more and 95% by mass or less, more preferably 80% by mass or more and 95% by mass or less, and most preferably 85% by mass or more and 95% by mass or less.

[B] Magnesium Salicylate In the lubricating oil composition of the present invention, magnesium salicylate is used as the metallic detergent. In addition to magnesium salicylate, other metallic detergents may be included, but preferably only magnesium salicylate is included.

Examples of magnesium salicylate include compounds represented by the following formula (1).

In formula (1), each R ¹ independently represents an alkyl group or alkenyl group having 14 to 30 carbon atoms, and n represents 1 or 2; Mg represents magnesium. 1 is preferable as n. When n=2, R ¹ may be a combination of different groups.
The magnesium salicylate may be carbonate overbased or borate overbased.

The content of magnesium salicylate contained in the lubricating oil composition of the present invention is 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.5% by mass or more, based on the total amount of the lubricating oil composition. More preferably, it is 1% by mass or more. The upper limit is 10% by mass or less, preferably 8% by mass or less, more preferably 5% by mass or less, and even more preferably 4% by mass or less. Specific ranges are 0.1% by mass to 10% by mass and 0.1% by mass to 3.0% by mass. It is preferably 0.2% by mass or more and 8% by mass or less, more preferably 0.5% by mass or more and 5% by mass or less, and still more preferably 1% by mass or more and 4% by mass or less. When the content of magnesium salicylate is 0.1% by mass or more, effective fuel saving performance and cleaning effect are obtained, and when the content of magnesium salicylate is 10% by mass or less, fuel saving performance and LSPI are reduced. effects are compatible.

The amount of magnesium derived from magnesium salicylate contained in the lubricating oil composition of the present invention is preferably 500 ppm by mass or more, more preferably 1000 ppm by mass or more, based on the total amount of the lubricating oil composition. The upper limit is preferably 2000 mass ppm or less, more preferably 1600 mass ppm or less. A specific range is preferably 500 mass ppm or more and 2000 mass ppm or less, more preferably 1000 mass ppm or more and 1600 mass ppm or less. By setting the content of magnesium within the above range, it is possible to keep the inside of the engine highly clean while suppressing the generation of LSPI.

(Base number)
The base value of the magnesium salicylate contained in the lubricating oil composition of the present invention is preferably 140 mgKOH/g or more, more preferably 180 mgKOH/g or more, and still more preferably 200 mgKOH/g or more, from the viewpoint of further improving fuel economy. be. The upper limit is preferably 500 mgKOH/g or less, more preferably 400 mgKOH/g or less, still more preferably 350 mgKOH/g or less. A specific range is preferably 140 mgKOH/g or more and 500 mgKOH/g or less, more preferably 180 mgKOH/g or more and 400 mgKOH/g or less, and still more preferably 200 mgKOH/g or more and 350 mgKOH/g or less. The base number is a value measured according to JIS K 2501 5.2.3.
The lower the base number, the less the inhibitory effect of MgCO ₃ , so the fuel economy can be further improved.

The lubricating oil composition of the present invention contains metal-based detergents other than magnesium salicylate, such as phenate-based detergents, sulfonate-based detergents, and salicylate-based detergents other than magnesium salicylate, within a range that does not impair the effects of the present invention. can, but preferably contains only magnesium salicylate.

The present inventors used magnesium salicylate as a detergent and further adjusted the HTHS viscosity at 150 ° C. to 1.6 mPa s or more and 2.5 mPa s or less, so that both the effect of reducing LSPI and the fuel saving performance can be achieved. It has now been found that it is possible to prepare a lubricating oil composition for internal combustion engines. Such a lubricating oil composition for an internal combustion engine could not be obtained by using a metallic detergent containing magnesium other than magnesium salicylate. This is surprising (Examples and Comparative Examples to be described later).

[C] Viscosity Index Improver The lubricating oil composition of the present invention preferably contains a viscosity index improver. As the viscosity index improver, those commonly used in the field of lubricating oil compositions for internal combustion engines can be used. Specifically, polymethacrylates, olefin copolymers, polybutene, polyisobutene, polyisobutylene, polystyrene, ethylene-propylene copolymers, styrene-diene copolymers and hydrogenated products thereof can be used. Polymethacrylate is preferred.

The weight average molecular weight of the viscosity index improver contained in the lubricating oil composition of the present invention is preferably 10,000 or more, more preferably 50,000 or more, still more preferably 100,000 or more. The upper limit is preferably 800,000 or less, more preferably 500,000 or less, even more preferably 400,000 or less. A specific range is preferably 10,000 or more and 800,000 or less, more preferably 50,000 or more and 500,000 or less, and still more preferably 100,000 or more and 400,000 or less.
The weight average molecular weight of a high molecular weight polymer means a value (molecular weight obtained by polystyrene conversion) determined by gel permeation chromatography (GPC).

The content of the viscosity index improver contained in the lubricating oil composition of the present invention is appropriately adjusted so that the HTHS viscosity of the lubricating oil composition at 150° C. is 1.6 mPa s or more and 2.5 mPa s or less. is preferred. When the lubricating oil composition of the present invention contains a viscosity index improver, the content thereof is 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.2% by mass or more, based on the total amount of the lubricating oil composition. It is 5% by mass or more, more preferably 1% by mass or more. The upper limit is 10% by mass or less, preferably 8% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less. A specific range is 0.1% by mass or more and 10% by mass or less, preferably 0.2% by mass or more and 8% by mass or less, more preferably 0.5% by mass or more and 5% by mass or less, and still more preferably 1% by mass. % or more and 3 mass % or less.

[D] Molybdenum-Based Friction Modifier The lubricating oil composition of the present invention preferably further contains (D) a molybdenum-based friction modifier as a friction modifier. As component (D), molybdenum dithiocarbamate (hereinafter sometimes simply referred to as MoDTC) is preferred.

As MoDTC, for example, a compound represented by the following formula (2) can be used.

In the above formula (2), R ² to R ⁵ may be the same or different, and are alkyl groups having 2 to 24 carbon atoms or (alkyl)aryl groups having 6 to 24 carbon atoms, preferably 4 to 4 carbon atoms. 13 alkyl groups or (alkyl)aryl groups having 10 to 15 carbon atoms. The alkyl group may be a primary alkyl group, secondary alkyl group or tertiary alkyl group, and may be linear or branched. In addition, "(alkyl)aryl group" means "aryl group or alkylaryl group". In the alkylaryl group, the substitution position of the alkyl group on the aromatic ring is arbitrary. X ¹ to X ⁴ are each independently a sulfur atom or an oxygen atom, and at least one of X ¹ to X ⁴ is a sulfur atom.

Molybdenum-based friction modifiers other than MoDTC include, for example, molybdenum dithiophosphate, molybdenum oxide, molybdic acid, molybdates such as ammonium salts, molybdenum disulfide, molybdenum sulfide, molybdenum sulfide, organic molybdenum compounds containing sulfur, and the like. can be mentioned.

When the lubricating oil composition of the present invention contains a molybdenum-based friction modifier, its content is 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0, based on the total amount of the lubricating oil composition. 0.2% by mass or more, more preferably 0.5% by mass or more. The upper limit is 10% by mass or less, preferably 8% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less. A specific range is 0.01% by mass to 10% by mass, preferably 0.1% by mass to 8% by mass, more preferably 0.5% by mass to 5% by mass, and still more preferably 0.5% by mass to 8% by mass. It is 5 mass % or more and 2 mass % or less.

The amount of molybdenum derived from the molybdenum-based friction modifier contained in the lubricating oil composition of the present invention is preferably 100 ppm by mass or more, more preferably 500 ppm by mass or more, based on the total amount of the lubricating oil composition. The upper limit is preferably 2000 mass ppm or less, more preferably 1000 mass ppm or less. A specific range is preferably 100 mass ppm or more and 2000 mass ppm or less, more preferably 500 mass ppm or more and 1000 mass ppm or less. When the molybdenum content is equal to or higher than the lower limit, the fuel economy performance and the LSPI suppression ability can be further enhanced. Moreover, when the molybdenum content is equal to or less than the above upper limit value, the storage stability of the lubricating oil composition can be enhanced.

(Other additives)
The lubricating oil composition of the present invention may further contain antiwear agents, antioxidants or dispersants.

As an antiwear agent, it is preferable to add zinc dialkyldithiophosphate (ZnDTP). Examples of zinc dialkyldithiophosphates include compounds represented by the following general formula (3).

R ⁶ to R ⁹ in the general formula (3) each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 24 carbon atoms, and at least one of R ⁶ to R ⁹ One is a linear or branched alkyl group having 1 to 24 carbon atoms. The alkyl group can be primary, secondary or tertiary.
In the lubricating oil composition of the present invention, one of these zinc dialkyldithiophosphates may be used alone, or two or more thereof may be used in combination. The zinc dialkyldithiophosphate is preferably a zinc dithiophosphate having a primary alkyl group (primary ZnDTP) or a zinc dithiophosphate having a secondary alkyl group (secondary ZnDTP). A material containing zinc dithiophosphate as a main component is preferable because it enhances wear resistance.

When the lubricating oil composition of the present invention contains zinc dialkyldithiophosphate, its content is 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.1% by mass or more, based on the total amount of the lubricating oil composition. It is 2% by mass or more, more preferably 0.5% by mass or more. The upper limit is 10% by mass or less, preferably 8% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less. A specific range is 0.01% by mass to 10% by mass, preferably 0.1% by mass to 8% by mass, more preferably 0.5% by mass to 5% by mass, and still more preferably 0.5% by mass to 8% by mass. It is 5 mass % or more and 2 mass % or less.

The amount of phosphorus derived from zinc dialkyldithiophosphate contained in the lubricating oil composition of the present invention is preferably 100 ppm by mass or more, more preferably 500 ppm by mass or more, based on the total amount of the composition. The upper limit is preferably 2000 mass ppm or less, more preferably 1000 mass ppm or less. A specific range is preferably 100 mass ppm or more and 2000 mass ppm or less, more preferably 500 mass ppm or more and 1000 mass ppm or less.

As the antioxidant, known antioxidants such as phenol antioxidants and amine antioxidants can be used. Examples include aminic antioxidants such as alkylated diphenylamine, phenyl-α-naphthylamine, alkylated-α-naphthylamine, 2,6-di-t-butyl-4-methylphenol, 4,4′-methylenebis( 2,6-di-t-butylphenol) and other phenolic antioxidants.
When the lubricating oil composition contains an antioxidant, its content is usually 5.0% by mass or less, preferably 3.0% by mass or less, and preferably 0, based on the total amount of the lubricating oil composition. .1% by mass or more, more preferably 0.5% by mass or more.

Dispersants include ashless dispersants such as succinimide or benzylamine.
When the lubricating oil composition contains a dispersant, its content is usually 5.0% by mass or less, preferably 0.1% by mass or more, based on the total amount of the lubricating oil composition.

The lubricating oil composition of the present invention can contain other additives commonly used in lubricating oils depending on the purpose in order to further improve its performance. Such additives may include additives such as antiwear or extreme pressure agents, pour point depressants, corrosion inhibitors, rust inhibitors, metal deactivators, antifoam agents, and the like.

(Lubricating oil composition for internal combustion engine)
The HTHS viscosity at 150° C. of the lubricating oil composition of the present invention is 1.6 mPa·s or more and 2.5 mPa·s or less. When the HTHS viscosity at 150°C is 2.5 mPa·s or less, good fuel economy performance can be obtained. If it is less than 1.6 mPa·s, lubricity may be insufficient.
The HTHS viscosity at 150°C of the lubricating oil composition of the present invention is 1.6 mPa s or more and 2.5 mPa s or less, preferably 1.6 mPa s or more and 2.4 mPa s or less, more preferably 1.6 mPa s. s or more and 2.3 mPa s or less, more preferably 1.6 mPa s or more and 2.2 mPa s or less, still more preferably 1.6 mPa s or more and 2.1 mPa s or less, most preferably 1.6 mPa s or more It is 2.0 mPa·s or less.
The HTHS viscosity at 150°C indicates the high-temperature high-shear viscosity at 150°C specified in ASTM D4683.

The viscosity index of the lubricating oil composition of the present invention is preferably 120 or more and 220 or less, more preferably 140 or more and 200 or less. When the viscosity index of the lubricating oil composition is 140 or more, the fuel economy performance can be further improved while maintaining a low HTHS viscosity at 150°C. Moreover, if the viscosity index of the lubricating oil composition exceeds 220, the evaporability may deteriorate.
As used herein, the viscosity index means a viscosity index measured according to JIS K 2283-1993.

The kinematic viscosity at 40° C. of the lubricating oil composition of the present invention is preferably 10 mm ² /s or more, more preferably 14 mm ² /s or more, still more preferably 16 mm ² /s or more, most preferably 18 mm ² /s or more. be. The upper limit is preferably 30 mm ² /s or less, more preferably 28 mm ² /s or less, even more preferably 25 mm ² /s or less, most preferably 22 mm ² /s or less. A specific range is preferably 10 mm ² /s or more and 30 mm ² /s or less, more preferably 14 mm ² /s or more and 28 mm ² /s or less, still more preferably 16 mm ² /s or more and 25 mm ² /s or less, most preferably is 18 mm ² /s or more and 22 mm ² /s or less. When the kinematic viscosity at 40° C. of the lubricating oil composition is 30 mm ² /s or less, sufficient fuel saving performance can be obtained. In addition, when the kinematic viscosity of the lubricating oil composition at 40° C. is 10 mm ² /s or more, it is possible to ensure the formation of an oil film at the lubricated portion and to reduce the evaporation loss of the lubricating oil composition.
As used herein, "kinematic viscosity at 40°C" means kinematic viscosity at 40°C measured according to ASTM D-445.

The kinematic viscosity at 100° C. of the lubricating oil composition of the present invention is preferably 3 mm ² /s or more, more preferably 4 mm ² /s or more. The upper limit is preferably 7 mm ² /s or less, more preferably 5 mm ² /s or less. A specific range is preferably 3 mm ² /s or more and 7 mm ² /s or less, more preferably 4 mm ² /s or more and 5 mm ² /s or less.

The density (ρ15) at 15°C of the lubricating oil composition of the present invention is preferably 0.860 or less, more preferably 0.850 or less. In this specification, the density at 15°C means the density measured at 15°C according to JIS K 2249-1995.

By using the lubricating oil composition of the present invention, the frequency of occurrence of LSPI can be reduced. In this specification, the LSPI occurrence frequency means the frequency of occurrence of abnormal combustion when the engine is running at low speeds.
In Non-Patent Document 1, the frequency of occurrence of LSPI when a lubricating oil composition is used for lubrication of an internal combustion engine has a positive correlation with the Ca content of the lubricating oil composition. It has been reported to have a negative correlation with P content and Mo content. More specifically, it is reported that the LSPI frequency index can be estimated by the following regression equation (6) based on the content of each element in the lubricating oil composition.
Formula (6)
LSPI frequency index = 6.59 x Ca - 26.6 x P - 5.12 x Mo + 1.69
(In formula (6), Ca represents the calcium content (mass%) in the composition, P represents the phosphorus content (mass%) in the composition, and Mo represents the molybdenum content (mass%) in the composition. %).)

The LSPI frequency index (calculated value) according to the formula (6) of the lubricating oil composition of the present invention is preferably 0 or less, more preferably 0.1 or less, more preferably 0.2 or less, It is more preferably 0.3 or less, more preferably 0.4 or less, still more preferably 0.5 or less, and most preferably 0.6 or less.

Regarding the evaporation loss of the lubricating oil composition of the present invention, the NOACK evaporation amount at 250° C. is preferably 30% by mass or less, more preferably 20% by mass or less, and 15% by mass or less. Especially preferred. If the NOACK evaporation amount of the lubricating base oil component exceeds 30% 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 the evaporation amount of lubricating oil measured according to ASTM D5800. The lower limit of the NOACK evaporation amount of the lubricating oil composition at 250° C. is not particularly limited, but is usually 5% by mass or more.

The present invention will be described below using examples. The present invention is not limited to the following embodiments. Unless otherwise specified, % indicates % by mass.

<Combination of lubricating oil>
Lubricating oil compositions for testing were prepared by blending base oils and additives at the blending ratios shown in Tables 1 and 2 for each example and each comparative example. The following evaluations were performed on the obtained lubricating oil composition for test. Evaluation results are shown in Tables 1 and 2.

(A) Base oil/base oil 1: Group III base oil (mineral oil) kinematic viscosity 3.3 mm ² /s (100°C), viscosity index 112
・Base oil 2: Group III base oil (mineral oil) kinematic viscosity 4.3 mm ² /s (100°C), viscosity index 123
Lubricating base oils were prepared by mixing base oils at the mass ratios shown in Tables 1 and 2. In the table, the numerical value of the base oil represents the mass ratio based on the total amount of the base oil.

(2) Additives Additives were added as described in Tables 1 and 2. The details of the additive are as follows. The blending amount of the additive is based on the total amount of the lubricating oil composition.
(B) Metallic detergent/metallic detergent 1: calcium salicylate (calcium content: 8.0% by mass, base number: 225 mgKOH/g)
- Metallic detergent 2: calcium sulfonate (calcium content: 12.5% by mass, base number: 320 mgKOH/g)
- Metallic detergent 3: magnesium salicylate (magnesium content is 7.4% by mass, base number: 342 mgKOH/g)
- Metallic detergent 4: magnesium salicylate (magnesium content is 6.1% by mass, base number: 292 mgKOH/g)
- Metallic detergent 5: magnesium salicylate (magnesium content is 4.3% by mass, base number: 218 mgKOH/g)
- Metallic detergent 6: magnesium salicylate (magnesium content is 8.3% by mass, base number: 390 mgKOH/g)
- Metallic detergent 7: magnesium sulfonate (magnesium content is 9.1% by mass, base number: 405 mgKOH/g)
(C) Viscosity index improver/Viscosity index improver 1: Polymethacrylate (weight average molecular weight 380,000)
(D) Friction Modifier/Friction Modifier 1: Molybdenum dithiocarbamate (molybdenum content 9.1% by mass, sulfur content 10.8% by mass)

Anti-wear agent 1: zinc dialkyldithiophosphate (zinc content 9.3% by mass, phosphorus content 9.3% by mass, sulfur content 17.6% by mass, secondary ZnDTP)
- Dispersant 1: Polyimide succinate (nitrogen content 1.75% by mass)
・Antioxidant 1: amine antioxidant ・Antioxidant 2: phenolic antioxidant

<Evaluation method>
(1) Fuel Saving Performance A motoring engine torque test was performed on each test lubricating oil composition. For each test lubricating oil composition, the torque required to rotate the output shaft of the DOHC engine (displacement 2.0 L) lubricated with the lubricating oil composition (oil temperature 95 ° C.) at a constant speed with an electric motor was measured. The measurement was performed at 1000 rpm, and the torque reduction rate with respect to the measured value in Comparative Example 1 was calculated. It means that the higher the torque reduction rate, the better the fuel efficiency.

(2) LSPI Frequency Calculation Value The LSPI frequency index for each test lubricating oil composition was calculated using the formula (6) described above. The results indicate that the lower the LSPI frequency index, the better the ability to suppress LSPI.

The evaluation results of each test lubricating oil composition are shown in Tables 1 and 2 below. The density at 15° C. of each test lubricating oil composition of Examples 1 to 4 and Comparative Examples 1 to 7 is 0.850 or less.

Examples 1 to 4, in which magnesium salicylate was used as a metallic detergent and the HTHS viscosity at 150°C was adjusted to 1.7, had improved fuel economy performance compared to Comparative Example 1, and the LSPI frequency calculated value was also lower. .
Comparative Example 1, in which calcium salicylate was used as the metallic detergent, gave a higher calculated LSPI frequency.
Comparative Example 2, in which the HTHS viscosity at 150° C. was adjusted to 2.6, was inferior to Comparative Example 1 in fuel saving performance.
Comparative Example 3, in which calcium salicylate was used as a metallic detergent and the HTHS viscosity at 150° C. was adjusted to 2.6, showed worse fuel economy performance and higher calculated LSPI frequency than Comparative Example 1.
Comparative Example 4, in which magnesium sulfonate was used as the metallic detergent, had poor fuel economy performance.
Comparative Example 5, in which calcium salicylate was used as the metallic detergent and the amount of the molybdenum friction modifier was reduced, showed a higher calculated LSPI frequency.
Comparative Example 5, in which calcium sulfonate was used as the metallic detergent, exhibited poor fuel economy performance and a high calculated LSPI frequency.
Comparative Example 6, in which calcium sulfonate was used as a metallic detergent and the HTHS viscosity at 150° C. was adjusted to 1.6, showed poor fuel economy performance and a high calculated LSPI frequency.

According to the lubricating oil composition for an internal combustion engine of the present invention, it is possible to provide a lubricating oil composition for an internal combustion engine that has both good fuel economy performance and an effect of reducing LSPI.

Claims

(A) a lubricating base oil having a kinematic viscosity at 100° C. of 2.5 mm 2 /s or more and 4.0 mm 2 /s or less, which contains one or more mineral base oils, and (B) the total amount of the lubricating oil composition A lubricating oil composition for an internal combustion engine containing 0.1% by mass or more and 10% by mass or less of magnesium salicylate on a basis,
The lubricating oil composition for an internal combustion engine, which has an HTHS viscosity of 1.6 mPa·s or more and 2.5 mPa·s or less at 150°C.
(B) the content of magnesium salicylate is 0.1% by mass or more and 3.0% by mass or less based on the total amount of the lubricating oil composition;
and (C) a viscosity index improver,
The lubricating oil composition for an internal combustion engine according to claim 1, wherein the content of the (C) viscosity index improver is 0.1% by mass or more and 10% by mass or less based on the total amount of the lubricating oil composition.
The lubricating oil composition for an internal combustion engine according to claim 1 or 2, further comprising (D) a molybdenum-based friction modifier as a friction modifier in an amount of 0.01% by mass or more and 10% by mass or less based on the total amount of the lubricating oil composition.
The lubricating oil composition for internal combustion engines according to any one of claims 1 to 3, wherein the magnesium salicylate has a base number of 350 mgKOH/g or less.
The lubricating oil composition for internal combustion engines according to any one of claims 1 to 4, wherein the HTHS viscosity at 150°C is 1.6 mPa·s or more and 2.0 mPa·s or less.
The lubricating oil composition for internal combustion engines according to any one of claims 1 to 5, wherein the LSPI frequency index calculated by the following formula (6) is 0 or less.
Formula (6)
LSPI frequency index = 6.59 x Ca - 26.6 x P - 5.12 x Mo + 1.69
(In formula (6), Ca represents the calcium content (mass%) in the composition, P represents the phosphorus content (mass%) in the composition, and Mo represents the molybdenum content (mass%) in the composition. %).).