JPH11181464A - Continuously variable transmission oil composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lubricating oil composition for a continuously variable transmission(CVT) having a high coefficient of friction capable of transmitting an engine power at a high output and excellent in abrasion preventing properties by compounding a base oil of a lubricating oil with specific plural compounds. SOLUTION: This lubricating oil composition is obtained by compounding a base oil of a lubricating oil (a known mineral oil and/or a known synthetic oil) with (A) 5-15 mass% polymethacrylate (dispersion type), (B) 0.5-3.0 mass% one or more kinds selected from a phenate of an alkaline earth metal and a sulfonate of the alkaline earth metal (a calcium salt, a magnesium salt or a barium salt), (C) 0.5-5.0 mass% imide compound (succinimide and/or a boron- containing succinimide) and (D) 0.5-3.0 mass% zinc alkyldithiophosphate (having a primary and/or a secondary alkyl group).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuously variable transmission oil composition, and more particularly to a lubricating oil composition for a metal belt type continuously variable transmission having a high friction coefficient, excellent durability of the friction coefficient, and low abrasion. About.

[0002]

2. Description of the Related Art In recent years, along with measures to prevent global warming, the emission of carbon dioxide has been reduced. For this reason, automobiles are also required to further improve fuel efficiency. The mainstream of automatic transmissions (ATs) for automobiles is a type that combines a torque converter, a wet clutch, a planetary gear, and the like. However, since this torque converter transmits power via automatic transmission fluid (ATF), the loss is large. For this reason, the power transmission loss is reduced by lock-up, but it is difficult to greatly reduce the transmission loss as long as a torque converter is used.

For this reason, there is a movement to adopt a continuously variable transmission (CVT) using a metal belt. The belt type CVT includes a driving pulley and a belt for transmitting power, and the belt includes an element and a steel strip holding the element. With this transmission, transmission loss can be significantly reduced. However, when the engine output is large, the belt and the pulley are likely to slip, so that it has been conventionally used in automobiles with a small displacement.
However, due to the demand for fuel economy, there has been a move to adopt it for high-power engines.

In order to efficiently transmit the engine output, it is necessary to prevent the pulley and the belt from slipping. However, when the pressure for sandwiching the belt is increased to prevent slippage, the belt is easily worn. For this reason, not only the improvement of the apparatus surface but also the lubricating oil is required to have a structure in which the belt and the pulley hardly slip and the belt and the pulley are hardly worn. In other words, there has been a demand for a lubricating material for preventing abrasion, but having a certain level of frictional force so that the pulley and the top do not slip for sufficient power transmission.

Japanese Patent Application Laid-Open No. 9-25491 discloses a CVT
In order to eliminate the "scratch phenomenon" of the present invention, the lubricating base oil should contain (a) an overbased detergent such as an alkylaryl sulfonate overbased with an alkali metal or an alkaline earth metal, and (b) diisooctyldithiophosphorus. An additive package consisting of a metal dialkyldithiophosphate such as zinc acid, (c) a sulfur-containing friction modifier such as sulfurized olefin and sulfurized fatty acid, (d) a fatty acid amide, and (e) a viscosity modifier such as polyolefin was added. A lubricating oil is disclosed.

Japanese Patent Application Laid-Open No. 9-78079 discloses an AST
Using the LFW-1 test method specified in MD2714, the vertical load was set to 200 lb, and the sliding speed was set to 0 to 1
The friction coefficient measured from the frictional force at each sliding speed was changed within the range of 00 cm / s, showing a positive friction characteristic in which the friction coefficient increased with the sliding speed, and the sliding speed was 2.
The coefficient of friction at a sliding speed of 5 cm or less is 0.12 to 0.14
Have been proposed. Specifically, it is a lubricating oil containing a sulfide ester, a metal salt-based detergent, zinc dialkyldithiophosphate, a phosphate ester, an imide compound, and polymethacrylate in a base oil of mineral oil or synthetic oil. By using this lubricating oil, large-capacity power transmission becomes possible, and the stick-slip phenomenon caused by slippage between metals can be suppressed.

Japanese Patent Application Laid-Open No. Hei 9-100487 discloses that a lubricating base oil comprises at least one sulfur-based extreme pressure agent selected from sulfurized fats and oils, thiocarbamates and thioterpenes, tricresyl phosphate, alkyl acid For continuously variable transmissions comprising at least one phosphorus extreme pressure agent selected from phosphate ester amine salts and alkenyl acid phosphate ester amine salts, and an alkaline earth metal detergent such as calcium phenate. A lubricating oil composition is disclosed. According to the document, excellent wear resistance and extreme pressure properties can be maintained, and a high friction coefficient can be maintained for a long time.

Japanese Unexamined Patent Publication No. 9-263782 discloses that a base oil containing a viscosity index improver, if necessary, can be added to an ashless dispersant such as a sulfonate or an imide compound, an acid amide, molybdenum dithiophosphate, or dithiocarbamine. A continuously variable transmission oil composition containing an organic molybdenum compound such as molybdenum acid and an amine-based antioxidant is disclosed. This composition is:
The minimum friction coefficient at 100 ° C. is 0.1 or more, and the ratio μs / μd of the friction coefficient μd at the sliding velocity V to the friction coefficient μs immediately before the sliding velocity becomes 0 is smaller than 1. It also states that it may contain fatty acid derivatives, partial ester compounds, sulfur-based antioxidants, and the like. Thereby, the friction coefficient can be maintained for a long time and the scratch phenomenon can be prevented.

[0009]

However, although the above documents focus on improving the coefficient of friction, in order to transmit high-power engine power, further improvement in terms of the coefficient of friction is required. Required.

[0010]

Means for Solving the Problems The present inventors have intensively studied a lubricating oil for a metal belt type CVT which can achieve both abrasion prevention and a high friction coefficient. As a result, a lubricating oil in which one or more selected from a polymethacrylate, an alkaline earth metal phenate and an alkaline earth metal sulfonate, an imide compound and a zinc alkyldithiophosphate are blended with a lubricating base oil, solves the above problem. I found that I was satisfied.

Here, the polymethacrylate is of a dispersion type, and its compounding amount is 5 to 15% by mass based on the continuously variable transmission oil. The alkaline earth metal phenate and the alkaline earth metal sulfonate are at least one selected from calcium salts, magnesium salts, and barium salts,
The compounding amount is 0.5 to 3.0% by mass based on the continuously variable transmission oil. The imide compound is a succinimide and / or
Or boron-containing succinimide, the blending amount,
It is 0.5 to 5.0% by mass based on the continuously variable transmission oil. The alkyl dithiophosphoric acid has a primary and / or secondary alkyl group, and its compounding amount is 0.5 to 3.0% by mass based on the continuously variable transmission oil. Only when such a combination is used, it has been found that abrasion prevention and a high coefficient of friction are exhibited, and the present invention has been completed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. As the lubricating base oil used in the present invention, known mineral oils and / or synthetic oils can be used. For example, by a known method, neutral oil or crude stock produced from crude oil as a raw material, bright stock, distillate at normal pressure is extracted with a solvent such as furfural, and the resulting raffinate is dewaxed with a solvent such as methyl ethyl ketone. And those obtained by further purifying them under high pressure to remove impurities such as sulfur. Examples of the synthetic oil include poly-α-olefin, polyhydric alcohol ester, and polyalkylene glycol.

In the present invention, it is preferable that the base material having a viscosity index of 120 or more contains 30% by mass or more, preferably 50% by mass or more. Examples of such a base material include waxes, highly hydrorefined oils and the like obtained by hydroisomerization, and synthetic oils. When the base material having a viscosity index of 120 or more is less than 30% by mass, the life of the continuously variable transmission oil may be reduced.

As the polymethacrylate, a dispersion type can be suitably used. Such a polymer can be obtained by copolymerization of an alkyl methacrylate monomer and a polar monomer. As the polar monomer, one or more selected from diethylaminoethyl methacrylate, 2-methyl-5-vinylpyrrolidone, N-vinylpyrrolidone, and morpholinoethyl methacrylate can be suitably used. The molar ratio between the alkyl methacrylate monomer and the polar monomer is 80:20 to 9 at which the dispersion effect is maximized.
A ratio of 5: 5 is preferred. The molecular weight of the polymer is, from the viewpoint of shear stability and the like, a number average molecular weight of 1
Those having a range of 0000 to 100,000 can be suitably used. The amount of polymethacrylate added is 5 to 15% by mass, and preferably 7 to 12% by mass, based on the total amount of the continuously variable transmission oil. If the content is less than 5% by mass, the low temperature startability and the wear prevention effect may be reduced. Further, if it exceeds 15% by mass, the wear prevention effect may be reduced, which is not preferable.

The alkaline earth metal phenate and the alkaline earth metal sulfonate may be at least one selected from the group consisting of calcium, magnesium and barium. However, at least one selected from calcium and magnesium is preferred in terms of improving the coefficient of friction.

The amount of at least one selected from alkaline earth metal phenates and alkaline earth metal sulfonates is from 0.5 to 3.0, based on the total amount of the continuously variable transmission oil.
%, Preferably 0.7 to 2.0% by mass. 0.
If the amount is less than 5% by mass, the durability of the coefficient of friction and the cleaning effect may be insufficient. On the other hand, if it exceeds 3.0% by mass, the coefficient of friction may be undesirably reduced.

The imide compound used in the present invention is a succinimide and / or a boron-containing succinimide. Those having an alkenyl group can be suitably used. This alkenyl succinimide is used for dispersing insolubles, sludge, and the like generated by oxidation of organic substances, but has a relatively small decrease in friction coefficient and an effect of reducing a change in friction coefficient with time.

The amount of succinimide and / or boron-containing succinimide added is 0.5% based on the total amount of the continuously variable transmission oil.
To 5.0% by mass, preferably 1.0 to 3.0% by mass. If the amount is less than 0.5% by mass, the coefficient of friction and the dispersing effect may be undesirably reduced. On the other hand, if it exceeds 5.0% by mass, the wear resistance is undesirably reduced.

This is a zinc compound of dithiophosphoric acid having two alkyl groups to be added to the base oil.
Primary alkyl group having 3 to 11 carbon atoms, 2 having 3 to 18 carbon atoms
One or more selected from a primary alkyl group and an aryl group substituted with an alkyl group having 3 to 18 carbon atoms. Among them, zinc dithiophosphate having a secondary alkyl group is preferable from the viewpoint of preventing abrasion. However, those having a primary alkyl group are excellent in stability against thermal and oxidative deterioration. Therefore, particularly when long-term stability of the continuously variable transmission oil is emphasized, 50% or more, preferably 70% or more of the alkyl group, More preferably, 90% or more of the primary alkyl group is used.

It is inevitable that dithiophosphoric acid having one alkyl group is mixed as an impurity, but it can be used as long as its solubility in the base oil is not a problem.

The amount of the zinc compound of dithiophosphoric acid having two alkyl groups is 0.5 to 3.0% by mass, and 0.7 to 2.0% by mass based on the total amount of the continuously variable transmission oil. More preferred. If the amount is less than 0.5% by mass, lubricity and oxidation stability may not be sufficient. Also, 3.
If it exceeds 0% by mass, further improvement in performance is not seen, which is not preferable.

In addition to the above additives, antioxidants, rust inhibitors, pour point depressants, metal deactivators and the like conventionally used in lubricating oils as long as the object of the present invention is not impaired. Can also be added as appropriate.

As the antioxidant, phosphorus-based antioxidants,
A phenolic antioxidant and an amine antioxidant are used alone or in combination. The addition amount of the antioxidant is about 0.1 to 3.0% by mass based on the total amount of the continuously variable transmission oil.
If the amount is less than 0.1% by mass, the antioxidant ability may be insufficient. On the other hand, when the content exceeds 3.0% by mass, sludge formation due to an increase in the concentration of the oxidative decomposition product may be caused, or the friction coefficient may be undesirably reduced.

As the phosphorus-based antioxidant, bis (2,4
-Di-t-butylphenyl) pentaerythritol diphosphite, phenyldiisodecylphosphite, diphenyldiisooctylphosphite, diphenyldiisodecylphosphite, triphenylphosphite, trisnonylphenylphosphite, tris-di-nonylphenylphosphite , Tris- (2,4-di-t-butylphenyl) phosphite, distearyl-pentaerythritol diphosphite, bis (nonylphenyl) pentaerythritol diphosphite, 4,4'-isopropylidene diphenol alkyl phosphite , 4,4 '
-Butylidenebis (3-methyl-6-t-butylphenyldi-tridecyl phosphite), 1,1,3-tris (2-methyl-4-di-tridecyl phosphite-5-
t-butylphenyl) butane, tetrakis (2,4-di-t-butylphenyl) -4,4'-bisphenylenediphosphite, 3,4,5,6-dibenzo-1,2-oxaphosphane- 2-oxide, trilauryl trithiophosphite, tris (isodecyl) phosphite,
Tris (tridecyl) phosphite, phenyldi (tridecyl) phosphite, diphenyltridecylphosphite, phenyl-bisphenol A pentaerythritol diphosphite, 3,5-di-t-butyl-
Examples thereof include 4-hydroxybenzylphosphonic acid diethyl ester, and one or more of these can be used.

Among these, aryl phosphites,
In particular, it is preferable that one aryl group has at least one or more, preferably two alkyl groups from the viewpoint of hydrolysis stability, and tris- (2,4-di-t-butylphenyl) phosphite, tris Nonylphenyl phosphite, tris- (mono and di mixed nonylphenyl) phosphite and the like can be suitably used. In particular, when an industrial grade reagent is used, the hydrocarbon group is 1 to 1.
It is inevitable that two things are mixed. However, as long as the solubility in the base oil is not a problem, it can be used as it is.

The phenolic antioxidants which can be used in the present invention include, for example, 2,6-di-t-butylphenol, 2-t-butyl-4-methoxyphenol, 2,4
-Dimethyl-6-t-butylphenol, 2,4-diethyl-6-t-butylphenol, 2,6-di-t-butyl-p-cresol, 2,6-di-t-butyl-4-
Ethylphenol, 2,6-di-t-butyl-4-hydroxymethylphenol, 2,6-di-t-butyl-4
-(N, N-dimethylaminomethyl) phenol, n-
Octadecyl-β- (4′-hydroxy 3 ′, 5-di-
t-butylphenyl) propionate, 2,4- (n-
(Octylthio) -6- (4-hydroxy3 ', 5'-di-t-butylanilino) -1,3,5-triazine, styrenated phenol, styrenated cresol, tocophenol, 2-t-butyl-6- ( 3'-t-butyl-
5′-methyl-2′-hydroxybenzyl) -4-methylphenyl acrylate, 2,2′-methylenebis (4
-Methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol), 2,2'-methylenebis (4-methyl-6-cyclohexylphenol), 2,2'- Dihydroxy-
3,3′-di (α-methylcyclohexyl) -5,5 ′
-Dimethyldiphenylmethane, 2,2'-ethylidene-
Bis (2,4-di-t-butylphenol), 2,2 ′
-Butylidene-bis (4-methyl-6-t-butylphenol), 4,4′-methylenebis (2,6-di-t-
Butylphenol), 4,4'-butylidenebis (3-
Methyl-6-t-butylphenol), 1,6-hexanediol bis [3- (3,5-di-t-butyl-4-
Hydroxyphenyl) propionate], triethylene glycol-bis-3-(-t-butyl-4-hydroxy-5-methylphenyl) propionate, N, N'-
Bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine, N, N'-hexamethylenebis- (3,5-di-t-butyl-4-hydroxy) hydrocinnamide , 2,2'-thiobis (4
-Methyl-6-t-butylphenol), 4,4′-thiobis (3-methyl-6-t-butylphenol),
2,2-thiodiethylenebis- [3 (3,5-di-t-
Butyl-4-hydroxyphenyl) propionate],
Bis [2-t-butyl-4-methyl-6- (3-t-butyl-5-methyl-2-hydroxybenzyl) phenyl] terephthalate, 1,1,3-tris (2-methyl-4-hydroxy- 5-t-butylphenyl) butane,
1,3,5-trimethyl-2,4,6-tris (3,5
-Di-t-butyl-4-hydroxybenzyl) benzene, tris (3,5-di-t-4-hydroxybenzyl) isocyanurate, 1,3,5-tris (4-t-
Butyl-3-hydroxy-2,6-dimethylbenzyl)
Isocyanurate, tetrakis [methylene-3-
(3 ', 5'-di-t-butyl-4-hydroxyphenyl) propionate] methane, calcium (3,5-di-t-butyl-4-hydroxybenzylmonoethylphosphonate), propyl gallate, gallic Octyl acid,
Lauryl gallate, 2,4,6-tri-t-butylphenol, 2,5-di-t-butylhydroquinone, 2,5
-Di-t-amylhydroquinone, 1,1,3-tris-
(2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris- (3,5-di-t-butyl-4-hi, do Roxybenzyl) benzene, 3,9-bis [2- {3- (3-t
-Butyl-4-hydroxy-5-methylphenyl) propionyloxy {-1,1-dimethylethyl] -2,
8,10-tetraoxaspiro [5,5] undecane and the like can be mentioned, and one or more of these can be used.

Of these, 2,6-di-tert-butyl-p-cresol and 2,2'-methylenebis (4-methyl-6-butyl) are preferred in terms of availability and use in lubricating oils.
t-butylphenol), 2,2′-methylenebis (4
-Ethyl-6-t-butyl-4-ethylphenol),
4,4′-methylenebis (2,6-di-t-butylphenol) and the like are preferable.

Examples of the amine antioxidants include p, p'-dioctyldiphenylamine, N-phenyl-N'-isopropyl-p-phenylenediamine, poly 2,2,4-trimethyl-1,2-dihydroquinoline,
6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, thiodiphenylamine, 4-amino-p
-Diphenylamine and the like, and one or more of these can be used.

As the metal deactivator, for example, benzotriazole, tolyltriazole, C2-C2
A benzotriazole derivative having 10 hydrocarbon groups,
Benzimidazole, an imidazole derivative having a C2-20 hydrocarbon group, a thiazole derivative having a C2-20 hydrocarbon group, 2-mercaptobenzothiazole, and the like, and one or more of these can be used. Can be used.

[0030]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples of a lubricating oil for a belt type CVT, but the present invention is not limited to only these examples.

(Test Method) In order to examine the friction coefficient of the continuously variable transmission oil, the stability of the friction coefficient and the lubricity, the SRV test (NLGI SPOKESMAN, 60 , 17 (199)
7). Is described in detail).
SUJ2 steel was used for the ball and the disk. Take a few milliliters of continuously variable transmission oil, perform a leveling operation for 10 minutes at an oil temperature of 40 ° C., a load of 10 N, amplitude of 2 mm and a frequency of 50 Hz.
The test was performed at 30 Hz for 30 minutes. Then, immediately after the start of this test, the friction coefficient after 10 minutes and 30 minutes, and the wear scar diameter after the end of the test were measured.

(Example 1) In the base oil of the following (a), (b)
9.0% by mass of polymethacrylate of (c), 1.0% by mass of calcium phenate of (c), 1.0% by mass of succinimide of (d), and 1.0% by mass of zinc alkyldithiophosphate of (e). 0% by mass and 0.4% by mass of the antioxidant (f) were added to obtain a continuously variable transmission oil composition. The concentration is a value based on the total amount of the continuously variable transmission oil. SRV
The results of the test are shown in Table 1, which shows not only a high coefficient of friction from the beginning of the test but also little wear. (A) Lubricating oil base oil: Hydroisomerized base oil 7 of wax
0% by mass and 30% by mass of a solvent dewaxed base oil were mixed and used. The kinematic viscosity of the former is 20 mm ² / s at 40 ° C.,
4.5 mm ² / s at 00 ° C., flash point 224 ° C.,
The sulfur content is 10 ppm, the aromatic component by NDM ring analysis is 0%, and the viscosity index is 142. The kinematic viscosity of the latter is 40 ° C
12 mm ² / s at 2.9 mm ^{2 at} 100 ° C.
/ S, flash point 190 ° C, sulfur content 0.08 mass%, N
According to DM ring analysis, the aromatic component was 5%, and the viscosity index was 80. (B) Dispersion-type polymethacrylate: nitrogen-based dispersion-type polymethacrylate (number-average molecular weight is about 53000) (c) Calcium phenate: base number is 240 mg KO
H / g (d) succinimide (e) zinc alkyldithiophosphate (ZnDTP): zinc dialkyldithiophosphate having a secondary alkyl group in which the alkyl group has 3 and 6 carbon atoms (f) Phosphorus antioxidant: Irganox L-180 manufactured by Ciba Specialty Chemicals (major component: Tris-
(2,4-di-t-butylphenyl) phosphite)

(Example 2) The alkyl group of ZnDTP in Example 1 was changed to a primary alkyl group having 8 carbon atoms, and the amount added was 1.
A continuously variable transmission oil composition was prepared in the same manner as in Example 1 except that the amount was changed to 3% by mass. The results of the SRV test are shown in Table 1. As in Example 1, not only the friction coefficient is high from the beginning of the test but also the wear is small.

(Example 3) A continuously variable transmission oil composition similar to that of Example 1 except that calcium sulfonate was used instead of calcium phenate of Example 1 and the addition amount was 0.8% by mass. Produced. The base number of calcium sulfonate is 30 mgKOH / g. Table 1 shows the results of the SRV test.

Comparative Example 1 A continuously variable transmission oil composition similar to that of Example 1 except that 0.5% by mass of sulfurized oil and 0.5% by mass of tricresyl thiophosphate was added instead of ZnDTP of Example 1. Was prepared. The results of the SRV test are shown in Table 1, but there is a problem that the coefficient of friction immediately after the start of the test is low.

Comparative Example 2 A continuously variable transmission oil composition similar to that of Example 1 was prepared except that the succinimide of Example 1 was omitted. The results of the SRV test are shown in Table 1, which showed that the coefficient of friction was low and unstable.

COMPARATIVE EXAMPLE 3 1.1% by mass of calcium salicylate was added in place of the calcium phenate of Example 1, to produce a continuously variable transmission oil composition similar to that of Example 1. The results of the SRV test are shown in Table 1, where the coefficient of friction was low.

(Comparative Example 4) A non-dispersible polymethacrylate (average molecular weight: 57000) was added in place of the dispersed polymethacrylate of Example 2 to prepare a continuously variable transmission oil composition similar to that of Example 2. . The results of the SRV test are shown in Table 1, where the coefficient of friction was low.

REFERENCE EXAMPLE Table 1 shows the SRV test results of a commercially available automatic transmission oil for a torque converter. The coefficient of friction was low.

[0040]

[Table 1]

[0041]

As described above, when the continuously variable transmission oil composition of the present invention is used, the friction coefficient is high, so that the power transmission loss is small and the wear is small. For this reason, it becomes possible to use it for a large-capacity belt type CVT, and it becomes possible to spread automobiles excellent in fuel efficiency.

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Claims (5)

[Claims] 1. A continuously variable lubricating base oil comprising at least one compound selected from the group consisting of polymethacrylates, alkaline earth metal phenates and alkaline earth metal sulfonates, an imide compound and zinc alkyldithiophosphate. Transmission oil composition. 2. The continuously variable transmission oil composition according to claim 1, wherein the polymethacrylate is of a dispersion type, and its compounding amount is 5 to 15% by mass based on the continuously variable transmission oil. 3. The alkaline earth metal phenate and the alkaline earth metal sulfonate are one or more selected from calcium salts, magnesium salts, and barium salts, and the compounding amount thereof is 0 based on a continuously variable transmission oil. 0.5-3.0
The continuously variable transmission oil composition according to any one of claims 1 and 2, wherein the composition is mass%. 4. The method according to claim 1, wherein the imide compound is succinimide and / or boron-containing succinimide, and the compounding amount thereof is 0.5 to 5.0% by mass based on a continuously variable transmission oil. The continuously variable transmission oil composition according to any one of claims 1 to 3. 5. The alkyl dithiophosphate according to claim 1, wherein the alkyl group is a primary and / or secondary alkyl group, and the compounding amount thereof is 0.5 to 3.0% by mass based on a continuously variable transmission oil. The continuously variable transmission oil composition according to any one of claims 1 to 4, wherein