Abstract: A lubricating oil composition may have a high flash point, a low pour point, and excellent electrical insulation, while having excellent cooling performance. Such a lubricating oil composition may include a base oil (A), wherein the base oil (A) includes at least one synthetic oil (A1) selected from a polyalkylene glycol having a specific degree of polymerization and a polyvinyl ether having a specific degree of polymerization.

Abstract: A viscosity index improver composition which has an excellent viscosity index improving effect. A viscosity index improver composition which includes a poly(meth)acrylate (A) including a constituent unit (Y) derived from a monomer (y) having a diol functional group, and a poly(meth)acrylate (B) including a constituent unit (Z) derived from a monomer (z) having a boronic acid ester.

Abstract: A lubricating oil additive composition that is suitable as a load bearing additive, and is excellent in wear resistance, extreme pressure property, and thermal stability, and a lubricating oil composition containing the lubricating oil additive composition. A lubricating oil additive composition containing a poly(meth)acrylate-based copolymer (X) containing a structural unit (a) derived from a particular alkyl (meth)acrylate (A), a structural unit (b) derived from a particular hydroxy group containing (meth)acrylate (B), and a structural unit (c) derived from a particular phosphorus-containing (meth)acrylate (C).

Abstract: A lubricating oil composition, including a base oil (P) and a copolymer (X). The copolymer (X) contains the following structural units (a) to (c): structural unit (a): a structural unit derived from a monomer (A) having a (meth)acryloyl group and a linear or branched alkyl group having 6 to 24 carbon atoms, structural unit (b): a structural unit derived from a monomer (B) having a (meth)acryloyl group and a polar group, and structural unit (c): a structural unit derived from a monomer (C) having a polymerizable functional group and a cyclic structural group. The copolymer (X) has a mass-average molecular weight (Mw) of 5,000 to 50,000, a content of the copolymer (X) in terms of resin content is 0.10% by mass to 2.5% by mass based on the total amount of the lubricating oil composition, and the lubricating oil composition has a 100° C. kinematic viscosity of 8.2 mm2/s or less.

Abstract: A lubricating oil additive composition containing a polymer-based compound may be excellent in solubility in a mineral oil and wear resistance, and favorable as a friction modifier. A lubricating oil composition may contain the additive composition. Such a lubricating oil additive composition may contain a copolymer (X) containing: (a) a structural unit derived from a monomer (A) having a (meth)acryloyl group and a linear or branched alkyl group having 6 to 24 carbon atoms; (b) a structural unit derived from a monomer (B) having a (meth)acryloyl group and a polar group; and (c) a structural unit derived from a monomer (C) having a polymerizable functional group and a cyclic structure group. The copolymer (X) may have a content of the structural unit (a) of 43% by mol or more based on the total structural units of the copolymer (X), and a mass average molecular weight (Mw) of 5,000 to 90,000.

Abstract: A polymer composition contains a comb-shaped polymer (X) containing the following structural units (a) to (c): (a): a structural unit derived from a short-chain alkyl (meth)acrylate (A) having a short-chain alkyl group having 1 to 5 carbon atoms; (b): a structural unit derived from a long-chain alkyl (meth)acrylate (B) having a long-chain alkyl group having 6 to 32 carbon atoms; and (c): a structural unit derived from a macromonomer (C), a content of the structural unit (a) being 70% by mass or more based on the total structural units of the comb-shaped polymer (X); and a hetero atom-containing base oil (Y). The hetero atom-containing base oil (Y) has a kinematic viscosity at 40° C. of 25 mm2/s or less.

Abstract: A lubricating oil additive composition that is suitable as a load bearing additive, and is excellent in wear resistance, extreme pressure property, and thermal stability, and a lubricating oil composition containing the lubricating oil additive composition. A lubricating oil additive composition containing a poly(meth)acrylate-based copolymer (X) containing a structural unit (a) derived from a particular alkyl (meth)acrylate (A), a structural unit (b) derived from a particular hydroxy group containing (meth)acrylate (B), and a structural unit (c) derived from a particular phosphorus-containing (meth)acrylate (C).

Abstract: A lubricating oil composition may have a high flash point, a low pour point, and excellent electrical insulation, while having excellent cooling performance. Such a lubricating oil composition may include a base oil (A), wherein the base oil (A) includes at least one synthetic oil (A1) selected from a polyalkylene glycol having a specific degree of polymerization and a polyvinyl ether having a specific degree of polymerization.

Abstract: A lubricating oil composition may be superior in cooling performance, ensure electrical insulation, and have a high flash point. Such a lubricating oil composition may include a base oil (A) including an ester-based synthetic oil (A1), the content of the ester-based synthetic oil (A1) is 30% by mass to 100% by mass based on the total amount of the base oil (A), the ester-based synthetic oil (A1) is one or more of an ester (A1-1) of a monohydric alcohol and a monobasic acid and an ester (A1-2) of a monohydric alcohol and a polybasic acid, and the base oil (A) satisfies requirements (1) to (3): Requirement (1): the kinematic viscosity at 40° C. is 2.00 mm2/s to 4.00 mm2/s. Requirement (2): the specific heat at 20° C. is 1.75 kJ/(kg·K) or less. Requirement (3): the density at 20° C. is 0.850 g/cm3 or more.

Abstract: A lubricating oil composition having a fluorescent compound that emits a fluorescent light. The fluorescent compound has a property of deteriorating with relevance to a deterioration of the lubricating oil composition. A deterioration measurement device having a light emitter that emits an irradiation light toward a measurement target object including a fluorescent compound, a light receiver, and a sensor. A deterioration measurement system having a lubricating oil composition and a deterioration measurement device.