JP6736037B2 - Lubricating oil composition for internal combustion engine - Google Patents

Description

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

In recent years, lubricating oils (engine oils) used in internal combustion engines such as automobile engines have been required to improve fuel economy in order to reduce CO ₂ emissions from automobiles. A method for improving the fuel economy of engine oil is to reduce the viscosity of the oil, but if the viscosity is excessively reduced, the engine may be worn. Therefore, a method of improving fuel economy by adding a friction modifier is being investigated instead.

For example, Patent Document 1 discloses a diesel engine oil composition containing a predetermined mineral oil-based base oil and various additives such as molybdenum dithiocarbamate-based friction modifiers for the purpose of improving fuel efficiency by reducing friction. There is.

JP, 2002-220597, A

An object of the present invention is to provide a lubricating oil composition for an internal combustion engine, which is excellent in fuel efficiency and corrosion resistance against copper and lead.

The present invention provides a lubricating oil composition for an internal combustion engine, which contains a lubricating base oil, an ashless friction modifier, and a boron-containing dispersant.

The lubricating oil composition preferably further comprises an overbased organic acid metal salt that is overbased with calcium borate.

The lubricating oil composition is preferably used as a diesel engine oil.

ADVANTAGE OF THE INVENTION According to this invention, the lubricating oil composition for internal combustion engines which is excellent in fuel-saving property and also the corrosion prevention property with respect to copper and lead can be provided.

The lubricating oil composition according to the present embodiment includes a lubricating base oil, (A) an ashless friction modifier (hereinafter also referred to as “(A) component”), and (B) a boron-containing dispersant (hereinafter “(B Also referred to as "component"). The lubricating oil composition according to the present embodiment is suitable as a lubricating oil composition for internal combustion engines.

The lubricating base oil is not particularly limited, and may be a base oil used for ordinary lubricating oils. Specifically, examples of the lubricating base oil include mineral base oils, synthetic base oils, or a mixture of both.

As the mineral oil-based base oil, a lubricating oil fraction obtained by distilling crude oil under atmospheric pressure and vacuum distillation is used for solvent degassing, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid. Examples include mineral oil-based base oils such as paraffin-based and naphthene-based base oils, normal paraffins, isoparaffins, and the like, which have been refined individually or in combination with two or more refining treatments such as washing and clay treatment. These mineral oil-based base oils may be used alone or in combination of two or more at any ratio.

Examples of preferable mineral oil-based base oils include the following base oils.
(1) Distillate oil of paraffin base crude oil and/or mixed base crude oil by atmospheric distillation (2) Distillation oil of paraffin base crude oil and/or mixed base crude oil under atmospheric pressure Vacuum distillation distillate of residual oil (WVGO) )
(3) Wax obtained by the lubricating oil dewaxing step and/or Fischer-Tropsch wax produced by the GTL process or the like (4) One or more mixed oils selected from the above (1) to (3) Mild Hydrocracking Processed Oil (MHC)
(5) Mixed oil of two or more kinds of oil selected from the above (1) to (4) (6) Deflaking off of the above (1), (2), (3), (4) or (5) Oil (DAO)
(7) Mild hydrocracking treated oil (MHC) of (6) above
(8) A mixed oil of two or more kinds of oils selected from the above (1) to (7) is used as a feedstock oil, and this feedstock oil and/or a lubricating oil fraction recovered from this feedstock oil is usually used. Lubricating oil obtained by refining with the refining method of

Here, the ordinary refining method is not particularly limited, and any refining method used in the base oil production can be adopted. Examples of ordinary purification methods include the following purification methods.
(A) Hydrorefining such as hydrocracking and hydrofinishing (b) Solvent refining such as furfural solvent extraction (c) Dewaxing such as solvent dewaxing and catalytic dewaxing (d) White clay with acid clay or activated clay Purification (e) Purification of chemicals (acid or alkali) such as sulfuric acid cleaning, caustic soda cleaning, etc. These purification methods may be used alone or in any combination of two or more and in any order.

Examples of synthetic base oils include poly-α-olefins or hydrides thereof, isobutene oligomers or hydrides thereof, isoparaffins, alkylbenzenes, alkylnaphthalenes, diesters (ditridecyl glutarate, di-2-ethylhexyl adipate, di-2-ethylhexyl azetate. Rate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc.), polyol ester (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, etc.), Examples thereof include polyoxyalkylene glycol, dialkyldiphenyl ether, polyphenyl ether and the like, and among them, poly α-olefin is preferable. Examples of the poly α-olefin include, for example, α-olefin oligomers or cooligomers (1-octene oligomers, decene oligomers, ethylene-propylene cooligomers, etc.) having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms, and their Examples include hydrides. These synthetic base oils may be used alone or in combination of two or more at any ratio.

The kinematic viscosity of the lubricating base oil at 40° C. is preferably 13.0 mm ² /s or more, and more preferably from the viewpoint of sufficient oil film formation, better lubricity, and smaller evaporation loss under high temperature conditions. It is 15.0 mm ² /s or more, more preferably 17.0 mm ² /s or more. The kinematic viscosity of the lubricating base oil at 40° C. is preferably 42.0 mm ² /s or less, more preferably 40.0 mm ² /s or less, from the viewpoint of improving low temperature viscosity characteristics and further excellent in fuel economy. It is preferably 38.0 mm ² /s or less.

The kinematic viscosity of the lubricating base oil at 100° C. is preferably 2.0 mm ² /s or more, more preferably from the viewpoint of sufficient oil film formation, better lubricity, and smaller evaporation loss under high temperature conditions. It is 3.0 mm ² /s or more, more preferably 3.5 mm ² /s or more. The kinematic viscosity of the lubricating base oil at 100° C. is preferably 8.0 mm ² /s or less, more preferably 7.0 mm ² /s or less, from the viewpoint of improving low temperature viscosity characteristics and further improving fuel economy. It is preferably 6.0 mm ² /s or less.

The viscosity index of the lubricating base oil is preferably 100 or more, more preferably 110 or more, further preferably 110 or more, from the viewpoint that the viscosity-temperature characteristics, heat/oxidation stability, and volatility-preventing properties become good and the friction coefficient can be further reduced. It is preferably 120 or more. The viscosity index of the lubricating base oil is preferably 180 or less, more preferably 170 or less, still more preferably 160 or less, from the viewpoint of excellent low temperature viscosity characteristics.

The kinematic viscosity and the viscosity index in the present invention mean the kinematic viscosity and the viscosity index respectively measured according to JIS K2283:2000.

The content of the lubricating base oil may be, for example, 50% by mass or more, 70% by mass or more, or 90% by mass or more based on the total amount of the lubricating oil composition.

Examples of the ashless friction modifier (A) include nitrogen-containing ashless friction modifiers and oxygen-containing ashless friction modifiers, with nitrogen-containing ashless friction modifiers being preferred. Specific examples of the component (A) include compounds such as amine, amide, imide, fatty acid ester, fatty acid, aliphatic alcohol, and aliphatic ether. These compounds are, for example, hydrocarbon groups having 6 to 30 carbon atoms, preferably alkyl groups or alkenyl groups having 6 to 30 carbon atoms, more preferably linear alkyl groups or linear alkenyl groups having 6 to 30 carbon atoms. Have at least one. The component (A) is preferably at least one selected from amines, amides and fatty acid esters, and more preferably at least one selected from amines and amides, from the viewpoint of further excellent fuel economy.

Examples of amines include linear or branched aliphatic monoamines or aliphatic polyamines, and alkylene oxide adducts thereof. The carbon number of these amines may be, for example, 6 to 30. The amine is preferably an amine represented by the following formula (1).
R ¹ -NH ₂ (1)
[In the formula (1), R ¹ is a hydrocarbon group having 6 to 30 carbon atoms, preferably an alkyl group or an alkenyl group having 6 to 30 carbon atoms, and more preferably a straight chain having 6 to 30 carbon atoms. It is an alkyl group or a straight-chain alkenyl group. ]
Specific examples of the amine represented by the formula (1) include oleylamine and stearylamine.

Examples of the amide include an amide of a linear or branched fatty acid and an aliphatic monoamine or an aliphatic polyamine. The carbon number of these amides may be, for example, 7 to 31. The amide is preferably an amide represented by the following formula (2).
R ¹ -C(=O)-NH ₂ (2)
[In Formula (2), R< ¹ > shows the same definition content as R< ¹ > in Formula (1). ]
Specific examples of the amide represented by the formula (2) include oleylamide and acrylamide.

Examples of the fatty acid ester include esters of a linear or branched fatty acid and an aliphatic monohydric alcohol or an aliphatic polyhydric alcohol. The fatty acid may be a saturated fatty acid or an unsaturated fatty acid. The carbon number of these fatty acid esters may be, for example, 7 to 31. The fatty acid ester is preferably an ester of a fatty acid and an aliphatic polyhydric alcohol, more preferably an ester of a linear fatty acid and an aliphatic polyhydric alcohol, and further preferably a linear unsaturated fatty acid. And an aliphatic polyhydric alcohol. The ester of these aliphatic polyhydric alcohols may be a complete ester or a partial ester, and is preferably a partial ester. Specific examples of the esters of these aliphatic polyhydric alcohols include glycerin monooleate.

The content of the component (A) is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and further preferably 0, based on the total amount of the lubricating oil composition, from the viewpoint of further excellent fuel economy. It is at least 3% by mass. The content of the component (A) is preferably 0.8% by mass or less, more preferably 0.7% by mass or less, further preferably 0% by mass based on the total amount of the lubricating oil composition from the viewpoint of excellent long-term storage stability. It is not more than 6% by mass. The content of the component (A) is preferably 0.1 to 0.8% by mass, and 0.1 to 0.8% by mass, based on the total amount of the lubricating oil composition, from the viewpoint of compatibility between fuel economy and long-term storage stability. 0.7 mass%, 0.1-0.6 mass%, 0.2-0.8 mass%, 0.2-0.7 mass%, 0.2-0.6 mass%, 0.3- It is 0.8% by mass, 0.3 to 0.7% by mass, or 0.3 to 0.6% by mass.

As the boron-containing dispersant (B), a nitrogen-containing compound such as a succinimide having an alkenyl group or an alkyl group derived from polyolefin, benzylamine, polyamine, Mannich base, etc., and boric acid to these nitrogen-containing compounds, Examples thereof include derivatives obtained by acting a boron compound such as borate. Among these, a derivative in which a boron compound such as boric acid or borate is allowed to act on a nitrogen-containing compound is preferable. The alkenyl group or alkyl group may be linear or branched, and may be a branched chain derived from an olefin oligomer such as a propylene group, a 1-butene group or an isobutylene group, or a co-oligomer of ethylene and propylene. It may be an alkyl group or a branched alkenyl group.

Specific examples of the component (B) include so-called monotype succinimide represented by the following formula (3) or so-called bis-type succinimide represented by the following formula (4), boric acid and boric acid. Examples thereof include modified succinimide modified with a boron compound such as a salt.

式（３）中、Ｒ^２は、炭素数４０〜４００のアルキル基又はアルケニル基を表し、好ましくは炭素数６０〜３５０のアルキル基又はアルケニル基を表す。Ｒ^２は、好ましくはポリブテニル基である。ｍは、１〜５の整数を表し、好ましくは２〜４の整数を表す。

In formula (3), R ² represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, and preferably an alkyl group or alkenyl group having 60 to 350 carbon atoms. R ² is preferably a polybutenyl group. m represents an integer of 1 to 5, preferably 2 to 4.

式（４）中、Ｒ^３及びＲ^４は、互いに同一でも異なっていてもよく、それぞれ炭素数４０〜４００のアルキル基又はアルケニル基を表し、好ましくは炭素数６０〜３５０のアルキル基又はアルケニル基を表す。Ｒ^３及びＲ^４は、好ましくは、それぞれポリブテニル基である。ｎは、０〜４の整数を表し、好ましくは１〜３の整数を表す。

In formula (4), R ³ and R ^{4, which} may be the same or different, each represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, and preferably an alkyl group or alkenyl group having 60 to 350 carbon atoms. Represents. R ³ and R ⁴ are preferably each a polybutenyl group. n represents an integer of 0 to 4, preferably an integer of 1 to 3.

The content of the component (B) is, based on the total amount of the lubricating oil composition, preferably 90 mass ppm or more, more preferably 100 mass ppm or more, further preferably 100 mass ppm or more, from the viewpoint of further excellent corrosion resistance to lead. It is preferably 110 mass ppm or more. The content of the component (B) is preferably 180 mass ppm or less, more preferably 170 mass ppm or less, further preferably 170 mass ppm or less in terms of boron element based on the total amount of the lubricating oil composition, from the viewpoint of further excellent fuel economy. It is 160 mass ppm or less. The content of the component (B) is preferably 90 to 180 mass in terms of boron element, based on the total amount of the lubricating oil composition, from the viewpoint of achieving a higher level of corrosion protection against lead and fuel efficiency. ppm, 90 to 170 mass ppm, 90 to 160 mass ppm, 100 to 180 mass ppm, 100 to 170 mass ppm, 100 to 160 mass ppm, 110 to 180 mass ppm, 110 to 170 mass ppm, or 110 to 160 mass ppm Is. The content of the component (B) (boron element conversion value) can be measured by the ICP elemental analysis method.

The lubricating oil composition preferably contains an overbased organic acid metal salt (hereinafter also referred to as “(C) component”) overbased with (C) calcium borate, from the viewpoint of further excellent corrosion resistance to lead. Further contains. Examples of the organic acid metal salt include alkaline earth metal sulfonates, alkaline earth metal salicylates, alkaline earth metal phenates, alkaline earth metal phosphonates, and the like. The alkaline earth metal may be magnesium, calcium, barium, preferably calcium. The component (C) is obtained, for example, by reacting the above organic acid metal salt, calcium hydroxide or calcium oxide, and boric acid or boric anhydride.

The base number of the component (C) is preferably 50 mgKOH/g or more, more preferably 100 mgKOH/g or more, still more preferably 150 mgKOH/g or more. The base number of the component (C) is preferably 500 mgKOH/g or less, more preferably 400 mgKOH/g or less, still more preferably 300 mgKOH/g or less. The base number in the present invention is 9. K in JIS K2501:2003. Means the base number measured by the perchloric acid method.

The content of the component (C) is, based on the total amount of the lubricating oil composition, preferably 100 mass ppm or more, more preferably 110 mass ppm or more, further preferably 110 mass ppm or more, from the viewpoint of further excellent corrosion resistance to lead. It is preferably 120 mass ppm or more. The content of the component (C) is, based on the total amount of the lubricating oil composition, preferably 350 mass ppm or less, more preferably 330 mass ppm or less, and further preferably 330 mass ppm or less, based on the total amount of the lubricating oil composition, from the viewpoint of further excellent corrosion resistance to lead. It is preferably 300 mass ppm or less. The content of the component (C) is preferably 100 to 350 mass ppm, 100 to 330 mass ppm, 100 in terms of calcium element based on the total amount of the lubricating oil composition, from the viewpoint of further excellent corrosion resistance to lead. -300 mass ppm, 110-350 mass ppm, 110-330 mass ppm, 110-300 mass ppm, 120-350 mass ppm, 120-330 mass ppm, or 120-300 mass ppm. The content (calcium element conversion value) of the component (C) can be measured by the ICP elemental analysis method.

The lubricating oil composition may further contain other additives. Other additives include viscosity index improvers, antiwear agents, antioxidants, defoamers, pour point depressants, corrosion inhibitors, rust inhibitors, demulsifiers, metal deactivators, and the like.

Examples of the viscosity index improver include poly(meth)acrylate-based viscosity index improvers, olefin copolymer-based viscosity index improvers, and styrene-diene copolymer-based viscosity index improvers. These viscosity index improvers may be either non-dispersion type or dispersion type, and are preferably non-dispersion type. The viscosity index improver is preferably a poly(meth)acrylate-based viscosity index improver, and more preferably a non-dispersed poly(meth), from the viewpoint of high viscosity index improving effect and excellent viscosity-temperature characteristics and low temperature viscosity characteristics. ) An acrylate-based viscosity index improver.

The pour point depressant may be, for example, poly(meth)acrylate, preferably poly(meth)acrylate having a weight average molecular weight of 10,000 to 300,000, and more preferably 50,000 to 200,000.

As the antiwear agent, phosphite (phosphite), phosphoric acid ester, and phosphorus-based antiwear agents such as amine salts, metal salts, and derivatives thereof, disulfide, polysulfide, sulfurized olefin, sulfurized oil and fat, etc. The sulfur-based antiwear agent can be used.

Examples of the antioxidant include ashless antioxidants such as phenol and amine, and metal antioxidants such as copper and molybdenum. Specifically, for example, phenol-based ashless antioxidants include 4,4′-methylenebis(2,6-di-tert-butylphenol) and 4,4′-bis(2,6-di-tert-). Butylphenol) and the like include amine-based ashless antioxidants such as phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, dialkyldiphenylamine and diphenylamine.

As the defoaming agent, for example, 100,000 mm kinematic viscosity at 25 ° C. is 1000 mm ² / s or more ² / s or less silicone oil, alkenylsuccinic acid derivatives, esters of polyhydroxy aliphatic alcohols and long-chain fatty acids, methyl salicylate And an ester of o-hydroxybenzyl alcohol.

Examples of the corrosion inhibitor include benzotriazole-based, tolyltriazole-based and imidazole-based compounds.

Examples of the rust preventive agent include alkenyl succinic acid ester, polyhydric alcohol ester, petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate and the like.

Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, and polyoxyethylene alkylnaphthyl ether.

Examples of the metal deactivator include imidazoline, pyrimidine derivatives, benzotriazole and derivatives thereof, and the like.

The content of other additives may be 0.01 to 20 mass% based on the total amount of the lubricating oil composition.

Kinematic viscosity at 40 ° C. of the lubricating oil composition, from the viewpoint of excellent lubricity, preferably 31.0 mm ² / s or more, more preferably 33.0 mm ² / s or more, more preferably 35.0 mm ² / s or more Is. Kinematic viscosity at 40 ° C. of the lubricating oil composition, to ensure low-temperature viscosity required, from the viewpoint of further improving the fuel economy, preferably 75.0 mm ² / s or less, more preferably 72.0 mm ² / s or less , And more preferably 70.0 mm ² /s or less.

Kinematic viscosity at 100 ° C. of the lubricating oil composition, from the viewpoint of excellent lubricity, preferably 5.0 mm ² / s or more, more preferably 7.0 mm ² / s or more, more preferably 8.0 mm ² / s or more Is. Kinematic viscosity at 100 ° C. of the lubricating oil composition, to ensure low-temperature viscosity required, from the viewpoint of further improving the fuel economy, preferably 14.0 mm ² / s or less, more preferably 13.0 mm ² / s or less And more preferably 12.0 mm ² /s or less.

The viscosity index of the lubricating oil composition is preferably 120 or more, more preferably 140 or more, further preferably 140 or more, from the viewpoint that the viscosity-temperature characteristic, the heat/oxidation stability, and the volatility prevention property are improved, and the friction coefficient can be further reduced. It is preferably 150 or more. The viscosity index of the lubricating base oil is preferably 270 or less, more preferably 260 or less, still more preferably 250 or less, from the viewpoint of excellent low temperature viscosity characteristics.

The elemental boron content in the lubricating oil composition is preferably 180 mass ppm or more, more preferably 190 mass ppm or more, and further preferably 200, based on the total amount of the lubricating oil composition, from the viewpoint of further excellent corrosion resistance to lead. It is mass ppm or more. The boron element content in the lubricating oil composition is preferably 440 mass ppm or less, more preferably 420 mass ppm or less, based on the total amount of the lubricating oil composition, from the viewpoint of further excellent corrosion resistance to lead and fuel economy. More preferably, it is 400 mass ppm or less. The elemental boron content can be measured by the ICP elemental analysis method.

The calcium element content in the lubricating oil composition is preferably 1800 mass ppm or more, more preferably 1900 mass ppm or more, and further preferably 2000, based on the total amount of the lubricating oil composition, from the viewpoint of further excellent corrosion resistance to lead. It is mass ppm or more. The calcium element content in the lubricating oil composition is preferably 2700 mass ppm or less, more preferably 2600 mass ppm or less, further preferably 2500, based on the total amount of the lubricating oil composition, from the viewpoint of further excellent corrosion resistance to lead. The mass is less than or equal to ppm. The calcium element content can be measured by the ICP elemental analysis method.

The lubricating oil composition according to this embodiment is suitably used as a lubricating oil composition for internal combustion engines. Examples of the internal combustion engine include a gasoline engine, a diesel engine, an oxygen-containing compound-containing fuel compatible engine, and a gas engine. The lubricating oil composition according to this embodiment is particularly preferably used as a diesel engine oil.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the examples.

Lubricating oil compositions having the compositions shown in Tables 1 and 2 were prepared using the base oils and additives shown below.
(Base oil)
Hydrorefined mineral oil (kinematic viscosity at 100° C.: 4.4 mm ² /s, viscosity index: 127)
(Additive)
A-1: glycerin monooleate A-2: oleylamine A-3: oleylamide a-1: molybdenum dithiocarbamate B-1: boric acid modified polybutenyl succinimide (weight average molecular weight of polybutenyl group: 7420, boron) Element content: 0.5% by mass)
C-1: Calcium salicylate overbased with calcium borate (base number: 190 mgKOH/g, calcium element content: 6.8% by mass)
D-1: Additive package containing calcium salicylate, calcium phenate, dialkyldithiophosphoric acid, etc. (boron element content: 0.12% by mass, calcium element content: 1.5% by mass)
E-1: Styrene-diene copolymer

(Fuel efficiency)
For each of the lubricating oil compositions of Examples 1 to 8 and Comparative Example 1, the fuel economy was evaluated by the friction coefficient by the SRV test and the HTHS viscosity at 100° C. (ASTM D4683). The results are shown in Table 3.
Regarding the coefficient of friction, "A" when the coefficient of friction is 0.150 or less, "B" when the coefficient of friction exceeds 0.150 and 0.155 or less, and "C" when the coefficient of friction exceeds 0.155. Was evaluated as
Regarding the HTHS viscosity at 100° C. (ASTM D4683), “A” indicates that the HTHS viscosity at 100° C. is 6.5 or less, and “B” indicates that the HTHS viscosity at 100° C. exceeds 6.5 and is 6.7 or less. The case where the HTHS viscosity at 100°C exceeds 6.7 was evaluated as "C". The HTHS viscosity at 150° C. of all Examples and Comparative Examples was 2.9.
If both the friction coefficient and the HTHS viscosity at 100° C. are evaluated as A or B, it can be said that the fuel economy is excellent.

(Corrosion protection against copper)
Each of the lubricating oil compositions of Examples 1 to 8 and Comparative Example 2 was evaluated for corrosion resistance to copper based on a corrosion oxidation stability test (JIS K2503:2010). However, the sample amount was 100 ml, the test temperature was 135° C., the test time was 168 hours, the air flow rate was 5 L/h, and the catalyst was copper, lead, or tin. The results are shown in Table 4. It can be said that the smaller the elution amount of copper (for example, 20 mass ppm or less), the more excellent the corrosion prevention property against copper.

(Corrosion protection against lead)
Each of the lubricating oil compositions of Examples 1 to 8 was evaluated for lead corrosion inhibition in accordance with a corrosion oxidation stability test (JIS K2503:2010). However, the sample amount was 100 ml, the test temperature was 135° C., the test time was 168 hours, the air flow rate was 5 L/h, and the catalyst was copper, lead, or tin. The results are shown in Table 5. It can be said that the smaller the elution amount of lead (for example, 150 mass ppm or less) is, the more excellent the corrosion prevention property against lead is.

Claims (2)

Lubricating base oil,
Ashless friction modifier,
A boron-containing dispersant,
Contain,
A lubricating oil composition for an internal combustion engine, further comprising an overbased organic acid metal salt overbased with calcium borate . The lubricating oil composition for internal combustion engines according to claim 1, which is used as a diesel engine oil.