Lubricating oil composition

Abstract

Provided is a lubricating oil composition, which has low viscosity but also prolonged anti-shudder life without reduction of intermetallic friction coefficient. The lubricating oil composition is characterized in comprising (A) a lubricating base oil, and (C) (C-1) a borated succinimide compound with a mass average molecular weight of 4,000-7,000 and (C-2) a borated succinimide compound with a mass average molecular weight of greater than 7,000-10,000.

Claims

1. A lubricating oil composition, comprising: (A) a lubricating base oil; and (C) (C-1) a boronated succinimide compound having a weight-average molecular weight of 600 to 7,000; (C-2) a boronated succinimide compound having a weight-average molecular weight of more than 7,000 and not more than 10,000; and (C-3) a non-boronated succinimide compound.

2. The lubricating oil composition according to claim 1, wherein part or all of component (A) comprises a poly(-olefin) or -olefin copolymer having a kinematic viscosity at 100 C. of 6 to 80 mm.sup.2/s in an amount of 5 to 30% by weight based on a total weight of the lubricating oil composition; and wherein the lubricating oil composition further comprises (B) a polymethacrylate having a weight-average molecular weight of 15,000 to 40,000.

3. The lubricating oil composition according to claim 1, wherein each of component (C-1) and component (C-2) contains 0.1 to 3% by weight of boron based on a weight of component (C-1) or component (C-2).

4. The lubricating oil composition according to claim 1, wherein a weight ratio of component (C-2) to component (C-1), i.e., (C-2)/(C-1) is 1 to 10.

5. The lubricating oil composition according to claim 1, wherein the lubricating oil composition has a kinematic viscosity at 100 C. of 3 to 10 mm.sup.2/s.

6. The lubricating oil composition according to claim 1, wherein the lubricating oil composition has a viscosity index of 150 or more.

7. The lubricating oil composition according to claim 1, further comprising (D) a metal detergent.

8. The lubricating oil composition according to claim 1, further comprising (E) an ether sulfolane compound.

9. The lubricating oil composition according to 2, wherein each of component (C-1) and component (C-2) contains 0.1 to 3% by weight of boron based on a weight of component (C-1) or component (C-2).

10. The lubricating oil composition according to claim 2, wherein a weight ratio of component (C-2) to component (C-1), i.e., (C-2)/(C-1) is 1 to 10.

11. The lubricating oil composition according to claim 3, wherein a weight ratio of component (C-2) to component (C-1), i.e., (C-2)/(C-1) is 1 to 10.

12. The lubricating oil composition according to claim 2, wherein the lubricating oil composition has a kinematic viscosity at 100 C. of 3 to 10 mm.sup.2/s.

Description

DESCRIPTION OF EMBODIMENTS

(1) The respective components will be described hereinbelow.

(2) (A) Lubricating Base Oil

(3) As the lubricating base oil in the present disclosure, a conventionally known lubricating base oil can be used, such as a mineral oil, synthetic oil, or a mixed oil thereof. In some embodiments, part or all of the lubricating base oil comprises a poly(-olefin) or -olefin copolymer having a kinematic viscosity at 100 C. of 6 to 80 mm.sup.2/s in an amount of 5 to 30% by weight based on the total weight of the lubricating oil composition, in which the lower limit is 6% by weight, or 8% by weight, and the upper limit is 25% by weight, or 20% by weight. When the content of the base oil is less than the above lower limit value, there cannot be obtained any sufficient viscosity index, i.e., both fuel consumption reduction and mechanical element protection performance, and when the content thereof is more than the above upper limit value, shear stability reduction and rubber compatibility deterioration (rubber shrinkage) can occur.

(4) The poly(-olefin) or -olefin copolymer has a kinematic viscosity at 100 C. of 6 to 80 mm.sup.2/s, 8 to 80 mm.sup.2/s, 8 to 60 mm.sup.2/s, or 9 to 40 mm.sup.2/s at 100 C. When the kinematic viscosity at 100 C. is less than the above lower limit value, there cannot be obtained viscosity index, i.e., both fuel consumption reduction and mechanical element protection performance, and when the kinematic viscosity at 100 C. is more than the above upper limit value, shear stability and of rubber compatibility are deteriorated (rubber shrinkage). Thus, both cases are not preferable.

(5) The poly(-olefin) or -olefin copolymer can be any (co)polymer or (co)oligomer of -olefin having the above-mentioned kinematic viscosity, and a conventionally known one can be used as the lubricating base oil. The -olefin is selected from, for example, linear or branched olefin hydrocarbons having 2 to 14 carbon atoms, or 4 to 12 carbon atoms, and examples thereof include 1-octene oligomer, 1-decene oligomer, ethylene-propylene oligomer, isobutene oligomer, and hydrogenated products thereof. Additionally, the poly(-olefin) or -olefin copolymer may be one manufactured using a metallocene catalyst. The weight-average molecular weight of the (co)polymer or (co)oligomer can be any as long as the kinematic viscosity at 100 C. satisfies the above range. For example, the weight-average molecular weight thereof is 1,000 to 10,000, or 1,100 to 7,000. The poly(-olefin) or -olefin copolymer may be used singly or in combination of two or more types thereof.

(6) The lubricating oil composition of the present disclosure may include other lubricating base oils in combination with the above poly(-olefin) or -olefin copolymer. These lubricating base oils are not particularly limited, and any of conventionally known mineral oil-based base oils and synthetic base oils other than the above poly(-olefin) or -olefin copolymer can be used.

(7) Examples of the mineral oil-based base oils include paraffin-based or naphthene-based lubricating base oils obtained by distilling crude oil at atmospheric pressure and under reduced pressure to produce a lubricating oil fraction and refining the lubricating oil fraction through appropriate combinations of refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, washing with sulfuric acid, and clay treatment; and lubricating base oils obtained by isomerization and dewaxing of a wax obtained by solvent dewaxing. The kinematic viscosity of the mineral oil-based base oils is, but not limited to, 1 to 5 mm.sup.2/s in order to obtain a lubricating oil composition having low viscosity.

(8) Examples of the synthetic base oils that can be used include isoparaffin, alkyl benzene, alkyl naphthalene, monoester, diester, polyol ester, polyoxyalkylene glycol, dialkyl diphenyl ether, polyphenyl ether, and GTL base oils. The kinematic viscosity of the synthetic base oils is not particularly limited. Additionally, it is also possible to use a poly(-olefin) or -olefin copolymer having a kinematic viscosity at 100 C. of less than 6 mm.sup.2/s or more than 80 mm.sup.2/s. In some embodiments, in order to obtain a lubricating oil composition having low viscosity, the kinematic viscosity of the synthetic base oils is 1 to 6 mm.sup.2/s.

(9) The base oils that can be used in combination may be used singly or in combination of two or more types thereof. When using in combination of two or more types, it is possible to use two or more mineral oil-based base oils, to use two or more synthetic base oils, and to use one or more mineral oil-based base oils and one or more synthetic base oils. In some embodiments, it is suitable to use a mineral oil-based base oil singly, to use two or more mineral oil-based base oils, to use a synthetic base oil having a kinematic viscosity at 100 C. of not less than 1 and less than 6 mm.sup.2/s singly, and to use two or more synthetic base oils having a kinematic viscosity at 100 C. of not less than 1 and less than 6 mm.sup.2/s.

(10) In addition, in order to obtain a lubricating oil composition having low viscosity, it is useful to have, as the entire lubricating base oil, a kinematic viscosity at 100 C. of 2 to 7 mm.sup.2/s, 2.3 to 6 mm.sup.2/s, or 2.5 to 5.6 mm.sup.2/s.

(11) (B) Viscosity Index Improver

(12) The lubricating oil composition of the present disclosure can include a conventionally known viscosity index improver. In some embodiments, the lubricating oil composition includes a polymethacrylate having a weight-average molecular weight of 15,000 to 40,000 as the viscosity index improver. The lower limit of the weight-average molecular weight is 17,000, or 18,000. The upper limit of the weight-average molecular weight is 38,000, or 36,000. When the weight-average molecular weight is less than the above lower limit value, the effect of improving the viscosity index is insufficient, and when the weight-average molecular weight is more than the above upper limit value, the effect of improving the viscosity index can be obtained whereas shear stability is deteriorated. Thus, both cases are not preferable. The content of the polymethacrylate in the lubricating oil composition is, but not limited to, 0.1 to 20% by weight, 1 to 15% by weight, or 2 to 10% by weight.

(13) The polymethacrylate may be used singly or in combination of two or more types. When used in combination of two or more types, the contents of the polymethacrylates are not limited. However, the total content of the polymethacrylates in the lubricating oil composition is 0.1 to 20% by weight, 1 to 15% by weight, or 2 to 10% by weight.

(14) The lubricating oil composition of the present disclosure may include comprise other viscosity index improvers in combination with the above-described polymethacrylate(s). Examples of the other viscosity index improvers include polymethacrylates having a weight-average molecular weight of less than 15,000, polymethacrylates having a weight-average molecular weight of more than 40,000, polyisobutylene and hydrogenated products thereof, hydrogenated styrene-diene copolymers, styrene-maleic anhydride ester copolymers, and polyalkylstyrene. When the lubricating oil composition comprises other viscosity index improver(s), the amount thereof in the lubricating oil composition is, in some embodiments, 0.1 to 15% by weight.

(15) (C) Boronated Succinimide Compound

(16) The lubricating oil composition of the present disclosure is characterized in that the composition comprises two types of specific boronated succinimide compounds as an ashless dispersant. Specifically, the present disclosure is characterized in that the lubricating oil composition comprises a combination of (C-1) a boronated succinimide compound having a weight-average molecular weight of 4,000 to 7,000, or 5,000 to 7,000 and (C-2) a boronated succinimide compound having a weight-average molecular weight of more than 7,000 and not more than 10,000, or 7,100 to 9,600. Hereinbelow, above component (C-1) may be referred to as first boronated succinimide compound, and above component (C-2) may be referred to as second boronated succinimide compound. The composition comprises component (C) in an amount of 0.5 to 3.0% by weight, 0.6 to 2.5% by weight, or 0.9 to 2.0% by weight, based on the total weight of the composition. When the content thereof is less than the above lower limit, anti-shudder performance cannot be obtained. When the content thereof is more than the above upper limit, low-temperature viscosity can be increased.

(17) The weight ratio of component (C-2) to component (C-1), i.e., (C-2)/(C-1) is, but not limited to, 1 to 10, 1.5 to 8, or 2 to 6. By including the components in a ratio within the above range, both friction coefficient and anti-shudder characteristics can be satisfied.

(18) When the amount of (C-1) is insufficient, there is a problem where regarding anti-shudder properties, characteristics at low temperature, for example, at 40 C. become insufficient, and this will be apparent early in durability testing. When the amount of (C-2) is insufficient, there is a problem where characteristics at high temperature, for example, at 120 C. become insufficient, and this will be apparent early in durability testing.

(19) The first and second boronated succinimide compounds in the present disclosure may be boronated succinimide compounds known as the ashless dispersant. A boronated succinimide compound includes a product obtained by modifying (boronating) a succinimide compound having at least one alkyl group or alkenyl group in a molecule thereof with boric acid, a borate, or the like. Examples of the alkyl group or alkenyl group include oligomers of olefins such as propylene, 1-butene, and isobutylene and co-oligomers of ethylene and propylene.

(20) More particularly, a succinimide compound is a compound obtained by adding succinic anhydride to a polyamine. The succinimide compound includes a mono-type succinimide compound and a bis-type succinimide compound, and either of which can be used. An example of a mono-type succinimide compound can be represented by following formula (1). An example of a bis-type succinimide compound can be represented by following formula (2):

(21) ##STR00001##

(22) In the above formulae, R.sup.1 each independently represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, m is an integer of 1 to 10, and n is an integer of 0 to 10. In some embodiments, a bis-type succinimide compound is used. The boronated succinimide compounds may be a combination of a mono-type and a bis-type, a combination of two or more mono-types, or a combination of two or more bis-types.

(23) More particularly, the boronated succinimide compound is a compound obtained by reacting a succinimide compound represented by formula (1) or (2) with a boron compound. Examples of the boron compound include a boric acid, a boric anhydride, a borate, a boric oxide, and a boron halide.

(24) The first boronated succinimide compound (C-1) has a weight-average molecular weight of 4,000 to 7,000. The weight-average molecular weight is 5,000 to 7,000, or 5,200 to 6,800. When the molecular weight of the first boronated succinimide compound is less than 4,000, anti-shudder characteristics are deteriorated.

(25) Note that, in the present disclosure, the weight-average molecular weight of the first boronated succinimide compound is a weight-average molecular weight measured by an RI (differential refractive index) detector, using a solvent of THF (tetrahydrofuran) and a packed column of styrene-divinylbenzene copolymer at a set temperature of 40 C. and a set flow rate of 1.0 mL/min, and expressed in terms of polystyrene.

(26) The boron content in the first boronated succinimide compound is, but not limited to, 0.1 to 3% by weight, 0.2 to 2.5% by weight, 0.2 to 2% by weight, or 0.2 to 1.5% by weight, based on the weight of the compound. The nitrogen content in the succinimide compound is, but not limited to, 0.3 to 10% by weight, 0.5 to 5% by weight, or 0.8 to 2.5% by weight, based on the weight of the compound.

(27) The content of the first boronated succinimide compound in the lubricating oil composition is, but not limited to, 0.05 to 2.00% by weight, 0.08 to 1.80% by weight, or 0.10 to 1.50% by weight, based on the total weight of the lubricating oil composition. When the content thereof is less than the lower limit value, sufficient detergency may not be able to be obtained, and when the content thereof is more than the upper limit value, sludge can occur.

(28) The second boronated succinimide compound (C-2) has a weight-average molecular weight of more than 7,000 and not more than 10,000. The weight-average molecular weight is 7,100 to 9,600, or 7,500 to 9,200. When the molecular weight of the second boronated succinimide compound is more than 10,000, low-temperature viscosity is deteriorated.

(29) Note that, in the present disclosure, the weight-average molecular weight of the second boronated succinimide compound is a weight-average molecular weight measured by an RI (differential refractive index) detector, using a solvent of THF (tetrahydrofuran) and a packed column of styrene-divinylbenzene copolymer at a set temperature of 40 C. and a set flow rate of 1.0 mL/min, and expressed in terms of polystyrene.

(30) The boron content in the second boronated succinimide compound is, but not limited to, 0.1 to 3% by weight, 0.2 to 2.5% by weight, 0.2 to 2% by weight, or 0.2 to 1.5% by weight, based on the weight of the compound. The nitrogen content in the succinimide compound is, but not limited to, 0.2 to 5.0% by weight, 0.3 to 2.5% by weight, or 0.5 to 2.0% by weight.

(31) The content of the second boronated succinimide compound in the lubricating oil composition is, but not limited to, 0.2 to 3.0% by weight, 0.4 to 2.5% by weight, or 0.6 to 2.0% by weight. When the content thereof is less than the lower limit value, sufficient detergency may not be able to be obtained, and when the content thereof is more than the upper limit value, low-temperature viscosity occurs.

(32) The lubricating oil composition of the present disclosure can further comprise other ashless dispersants in combination with components (C-1) and (C-2). A typical example of another ashless dispersant includes (C-3) a non-boronated succinimide compound.

(33) A non-boronated succinimide compound is a succinimide compound having at least one alkyl group or alkenyl group in a molecule thereof. An example thereof is the succinimide compound represented by formula (1) or (2) above. As the succinimide compound, either a mono-type succinimide compound or a bis-type succinimide compound can be used. In some embodiments, a bis-type succinimide compound is used. The succinimide compound may be a combination of a mono-type and a bis-type, a combination of two or more mono-types, or a combination of two or more bis-types.

(34) When the lubricating oil composition comprises a succinimide compound containing no boron, the content thereof in the lubricating oil composition is 2% by weight or less, or 1% by weight or less.

(35) In some embodiments, the lubricating oil composition of the present disclosure further comprises (D) a metal detergent and/or (E) an ether sulfolane compound, in addition to above components (A) to (C).

(36) (D) Metal Detergent

(37) A metal detergent includes detergents containing an alkali metal or an alkaline earth metal. Examples thereof include, but are not limited to, sulfonates containing an alkali metal or alkaline earth metal, salicylates containing an alkali metal or alkaline earth metal, and phenates containing an alkali metal or alkaline earth metal. The alkali metal or alkaline earth metal include, but are not limited to, magnesium, barium, sodium, and calcium.

(38) In some embodiments, used sulfonates containing an alkali metal or alkaline earth metal include, but are not limited to, calcium sulfonate and magnesium sulfonate.

(39) In some embodiments, used salicylates containing an alkali metal or an alkaline earth metal include, but are not limited to, calcium salicylate and magnesium salicylate.

(40) In some embodiments, used phenates containing an alkali metal or an alkaline earth metal include, but are not limited to, calcium phenate and magnesium phenate.

(41) The amount of the alkali metal or alkaline earth metal contained in the metal detergent is, but not limited to, 0.1 to 20% by weight, 0.5 to 15% by weight, or 1.0 to 15% by weight.

(42) The metal detergent has a total base number of, but not limited to, 10 to 500 mgKOH/g, 50 to 400 mgKOH/g, or 150 to 400 mgKOH/g. Particularly, when the total base number thereof is 200 to 400 mgKOH/g, 300 to 400 mgKOH/g, 310 to 400 mgKOH/g, it is useful since high detergent effect is obtained, and the occurrence of sludge can be suppressed.

(43) The content of the metal detergent in the lubricating oil composition is, but not limited to, 0 to 5% by weight, 0.1 to 2% by weight, or 0.2 to 1% by weight.

(44) The metal detergent may be used singly or in combination of two or more types. When used in combination, the combinations of the metal detergents include, but are not limited to, a combination of two or more sulfonate compounds, a combination of two or more salicylate compounds, a combination of two or more phenate compounds, a combination of at least one sulfonate compound and at least one salicylate compound, a combination of at least one sulfonate compound and at least one phenate compound, and a combination of at least one salicylate compound and at least one phenate compound.

(45) (E) Ether Sulfolane Compound

(46) The lubricating oil composition of the present disclosure may further ensure appropriate sealing rubber swellability by comprising an ether sulfolane compound. The ether sulfolane compound is a compound as follows:

(47) ##STR00002##

(48) In the above formula, R is an alkyl group having 1 to 20 carbon atoms, or an alkyl group having 8 to 16 carbon atoms.

(49) The content of the ether sulfolane compound in the lubricating oil composition is 0 to 5% by weight, 0.1 to 2% by weight, or 0.2 to 1% by weight.

(50) The lubricating oil composition of the present disclosure may further comprise additives other than above components (B) to (E). Examples of the other additives include oil agents, anti-wear agents, extreme pressure agents, rust inhibitors, friction modifiers, antioxidants, corrosion inhibitors, metal deactivators, pour point depressants, antifoaming agents, colorants, and packaged additives for automatic transmission oil. It is also possible to add various packaged additives for lubricating oil that contain at least one of the above additives.

(51) The kinematic viscosity at 100 C. of the lubricating oil composition of the present disclosure is, but not limited to, 3 to 10 mm.sup.2/s, 3 to 8 mm.sup.2/s, 4 to 7.5 mm.sup.2/s, or 4 to 6 mm.sup.2/s. When the kinematic viscosity at 100 C. of the lubricating oil composition is less than the above lower limit value, sufficient friction coefficient may not be able to be obtained. Additionally, when it is more than the above upper limit value, anti-shudder characteristics may be deteriorated.

(52) The viscosity index of the lubricating oil composition of the present disclosure is, but not limited to, 150 or more, or 160 or more. When the viscosity index of the lubricating oil composition is less than the above lower limit value, sufficient low-temperature characteristics may not be able to be obtained. In some embodiments, the upper limit is, but not limited to, 250.

(53) The lubricating oil composition of the present disclosure has a sufficiently large metal-to-metal friction coefficient even at lowered viscosity, and also can effectively obtain anti-shudder characteristics. In addition, as described above, shear stability can also be ensured by additionally specifying the structures of the base oil and the viscosity index improver in accordance with the present disclosure. Furthermore, adding an ether sulfolane compound can ensure appropriate swellability of sealing rubber. In some embodiments, a metal detergent having a total base number of 200 to 400 mgKOH/g is used since the occurrence of sludge can be suppressed while ensuring detergency. The lubricating oil composition of the present disclosure may be suitably used for continuously variable transmissions.

EXAMPLES

(54) Hereinafter, the present disclosure will be described in more detail by illustrating Examples and Comparative Examples. However, the present disclosure is not limited to the following Examples.

(55) Respective components used in Examples and Comparative Examples are listed below. The respective components below were mixed in compositions listed in Table 1 or 2 to prepare lubricating oil compositions. In the following description, KV100 means kinematic viscosity at 100 C., VI means viscosity index, and PMA means polymethacrylate.

(56) (A) Lubricating Base Oil

(57) Mineral oil 1: highly hydrogenated refined paraffin-based base oil (KV100=3.1 mm.sup.2/s, VI=112) Mineral oil 2: highly hydrorefined paraffin-based base oil (KV100=4.2 mm.sup.2/s, VI=122) Mineral oil 3: highly hydrorefined paraffin-based base oil (KV100=4.2 mm.sup.2/s, VI=134) Mineral oil 4: hydrorefined paraffin-based base oil (KV100=2.2 mm.sup.2/s, VI=109) Mineral oil 5: hydrorefined paraffin-based base oil (KV100=2.5 mm.sup.2/s, VI=99) Synthetic base oil 1: poly(-olefin) (KV100=4.1 mm.sup.2/s, VI=126) Synthetic base oil 2: poly(-olefin) (KV100=10 mm.sup.2/s, VI=137) Synthetic base oil 3: poly(-olefin) (KV100=40 mm.sup.2/s, VI=147) Synthetic base oil 4: ethylene--olefin copolymer (KV100=10 mm.sup.2/s, VI=150) Synthetic base oil 5: ethylene--olefin copolymer (KV100=40 mm.sup.2/s, VI=155) Synthetic base oil 6: ethylene--olefin copolymer (KV100=100 mm.sup.2/s, VI=165)
(B) Viscosity Index Improver PMA-based viscosity index improver 1 (Mw=30,000)
(C) Boronated Succinimide Compound
(C-1) Boronated succinimide compound 1 (Mw=5,600, B: 0.34% by weight, N=1.58% by weight, containing a polyisobutenyl group) Boronated succinimide compound 3 (Mw=4,600, B: 1.8% by weight, N=2.35% by weight, containing a polyisobutenyl group)
(C-2) Boronated succinimide compound 2 (Mw=8,500, B: 0.23% by weight, N=0.88% by weight, containing a polyisobutenyl group)
(D) Metal Detergent Ca sulfonate (total base number: 350 mgKOH/g) Ca salicylate (total base number: 300 mgKOH/g) Mg salicylate (total base number: 400 mgKOH/g)
(E) Ether Sulfolane Compound LUBRIZOL 730 (a compound of the following formula, in which R.sup.1 is C.sub.10H.sub.21)

(58) ##STR00003##
(F) Other Additives

(59) Anti-wear agent, friction modifier, antioxidant, defoaming agent, metal deactivator, and colorant

(60) TABLE-US-00001 TABLE 1 Composition (% by weight) Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 (A) Mineral oil 1 70.39 70.39 83.08 83.08 70.39 70.39 70.39 70.99 Mineral oil 2 34.28 Mineral oil 3 25.12 Mineral oil 4 36.11 Mineral oil 5 45.27 71.82 Synthetic base oil 1 Synthetic 20.95 20.95 20.95 20.95 20.95 20.95 20.95 20.95 base oil 2 Synthetic 8.26 base oil 3 Synthetic 20.95 base oil 4 Synthetic 8.26 base oil 5 Kinematic 4.0 4.0 4.0 3.7 4.0 4.0 4.0. 4.0 4.0 3.0 4.0 viscosity KV100 of entire base oil (B) Viscosity index 3.08 3.08 3.08 3.08 3.08 3.08 3.08 3.08 3.08 1.65 3.08 improver 1 (C) Boronated 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49 succinimide compound 2 Boronated 0.33 0.33 0.33 0.33 0.33 0.33 0.33 0.33 0.33 0.33 0.33 succinimide compound 1 Boronated succinimide compound 3 (D) Calcium 0.16 0.16 0.16 0.16 0.16 0.16 0.16 0.16 sulfonate Calcium 0.16 0.03 salicylate Magnesium 0.13 0.16 salicylate (E) Ether sulfolane 0.60. 0.60 0.60 0.60 0.60 0.60 0.60 0.80 0.60 0.60 Other additives 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00

(61) TABLE-US-00002 TABLE 2 Composition (% by weight) Comp. Ex. 1 (A) Mineral oil 1 70.39 Mineral oil 5 Synthetic base oil 1 Synthetic base oil 2 20.95 Synthetic base oil 6 Kinematic viscosity KV100 of entire base oil 3.7 (B) Viscosity index improver 1 3.08 Ashless Boronated succinimide compound 2 dispersant Boronated succinimide compound 1 0.33 Boronated succinimide compound 3 1.49 (D) Calcium sulfonate 0.16 (E) Ether sulfolane 0.60 Other additives 3.00

(62) Various properties of the respective lubricating oil compositions were measured according to the following methods. Tables 3 and 4 give the results.

(63) (1) Kinematic Viscosity at 100 C. (KV100)

(64) Test method: measured according to ASTM D445.

(65) (2) Viscosity Index

(66) Test method: measured according to ASTM D2270.

(67) (3) Shear Stability

(68) Test method: according to JASO M347-2014, measured a viscosity at 100 C. after 10 hours to determine a rate of change from a viscosity before starting the test.

(69) (4) Anti-Shudder Life

(70) Test method: according to JASO M349-2012, measured a time during which any of values of d/dv (average in 1.0 to 2.0 m/s) evaluated at 40 C., 60 C., 80 C., and 120 C. was below 210.sup.3.

(71) (5) Friction Coefficient (Comparison with a Commercially Available Product)

(72) Test was performed by an SRV friction and wear testing machine manufactured by Optimol Co. Ltd., using a SUJ ball (diameter: 10 mm) and a SUJ disc (24 mm in diameter6.9 mm in height, lapping treatment) manufactured by Optimol Co. Ltd. under a load of 100 N, at a temperature of 100 C., at a frequency of 50 Hz, and at an amplitude of 0.5 mm to obtain an average value of friction coefficients after 30 minutes and then obtain a ratio relative to the commercially available oil.

(73) (6) Rubber Swellability

(74) Test method: according to ASTM D471, immersed a C-type dumbbell-shaped ACM rubber (T945, manufactured by NOK Corporation) in a sample oil at 150 C. to determine a rate of volume change after 70 hours.

(75) Note that, in Comparative Example 2 of Table 4, a commercially available lubricating oil composition for transmission was evaluated.

(76) TABLE-US-00003 TABLE 3 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 [C2]/[C1] 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 Viscosity (KV100) of 5.5 5.5 5.5 5.2 5.5 5.5 5.5 5.5 5.5 4.5 5.5 lubricating oil composition VI 163 168 170 168 163 163 163 170 168 151 163 Shear stability 4 4 4 4 4 4 4 4 4 4 4 Anti-shudder life 450 450 450 450 450 450 450 450 450 450 450 Friction coefficient 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Rubber swellability 5 5 5 5 5 5 5 5 5 5 1

(77) TABLE-US-00004 TABLE 4 Comp. Comp. Ex. 1 Ex. 2 [C2]/[C1] 0 Viscosity (KV100) of lubricating oil composition 5.2 7.2 VI 161 201 Shear stability 4 21 Anti-shudder life 20 200 Friction coefficient 1.0 1.0 Rubber swellability 5 6

(78) As indicated in Examples 1 to 11 described in Tables 3 and 4, the lubricating oil compositions of the present disclosure may prolong anti-shudder life without lowering metal-to-metal friction coefficient, although having low kinematic viscosities at 100 C. Additionally, as can be seen from a comparison between Examples 1 to 11 and Comparative Example 1, additionally specifying the structure of component (A) and the structure of component (B) enables provision of lubricating oil compositions having higher shear stability in addition to the above advantageous effect. Furthermore, a comparison between Examples 1 to 10 and Example 11 indicates that specifying the structure of component (A) and including (E) ether sulfolane can further improve swellability of sealing rubber in addition to the above effect.

INDUSTRIAL APPLICABILITY

(79) The lubricating oil composition of the present disclosure may be particularly suitable to use for automobile transmissions, particularly for continuously variable transmissions.