Provided are a viscosity modifier for lubricating oils for obtaining an additive composition for lubricating oils having excellent fluidity in a wide temperature range from low temperature to high temperature; and said additive composition for lubricating oils. Further provided are a viscosity modifier for lubricating oils for obtaining a lubricating oil composition capable of reducing viscosity in good balance in a wide temperature range from low temperature to high temperature; and said lubricating oil composition. The viscosity modifier for lubricating oils includes an ethylene -olefin copolymer (A) which includes 30 to 50 mole % of structural units derived from at least one -olefin selected from -olefins having 4 and 5 carbon atoms and 50 to 70 mole % of structural units derived from ethylene (with the proviso that the total of all structural units of said copolymer is 100 mole %) and which satisfies specific requirements (a), (b), and (c).

A composition comprising a sheared antifoam solution/mixture with a mean particle size from about 0.01 microns to about 0.5 microns and a maximum particle size of less than about 1 micron. In this composition the sheared antifoam solution/mixture comprises antifoam solution/mixture comprising an antifoam and a base stock.

The present disclosure concerns engine lubricant compositions including at least one base oil, at least one viscosity index improver polymer and at least one polyalkylene glycol, obtained by polymerization or copolymerization of alkylene oxides comprising from 3 to 8 carbon atoms, including at least one butylene oxide, the quantity of polyalkylene glycol being from 1 to 28% by mass with respect to the total mass of lubricant composition. Using at least one polyalkylene glycol, obtained by polymerization or copolymerization of alkylene oxides including from 3 to 8 carbon atoms, further including at least one butylene oxide in a base oil improves engine cleanliness while not increasing, or indeed while decreasing, the consumption of petrol or diesel fuels by the engine.

The present disclosure concerns engine lubricant compositions including at least one base oil, at least one viscosity index improver polymer and at least one polyalkylene glycol, obtained by polymerization or copolymerization of alkylene oxides comprising from 3 to 8 carbon atoms, including at least one butylene oxide, the quantity of polyalkylene glycol being from 1 to 28% by mass with respect to the total mass of lubricant composition. Using at least one polyalkylene glycol, obtained by polymerization or copolymerization of alkylene oxides including from 3 to 8 carbon atoms, further including at least one butylene oxide in a base oil improves engine cleanliness while not increasing, or indeed while decreasing, the consumption of petrol or diesel fuels by the engine.

An engine oil composition includes a star polymer (A) and a poly(alkyl (meth)acrylate) (B) as a viscosity index improver, and has a viscosity index of 185 to 230, the star polymer (A) having a star structure and having a weight average molecular weight of 100,000 to 1,000,000, the star structure being a structure in which polymer chains branch from a center of the polymer, the polymer chains being obtained by copolymerization and hydrogenation of an aromatic vinyl compound monomer and a conjugated diene monomer, the poly(alkyl (meth)acrylate) (B) having a weight average molecular weight of 200,000 to 600,000, the content (M.sub.A) of the star polymer (A) in the engine oil composition being 0.10 to 2.00 mass % based on the total mass of the engine oil composition, the content (M.sub.B) of the poly(alkyl (meth)acrylate) (B) in the engine oil composition being 0.50 to 6.00 mass % based on the total mass of the engine oil composition, and the ratio M.sub.A/M.sub.B being 0.10 to 1.00. The engine oil composition can significantly improve fuel efficiency, and is suitably used for a diesel engine.

An engine oil composition includes a star polymer (A) and a poly(alkyl (meth)acrylate) (B) as a viscosity index improver, and has a viscosity index of 185 to 230, the star polymer (A) having a star structure and having a weight average molecular weight of 100,000 to 1,000,000, the star structure being a structure in which polymer chains branch from a center of the polymer, the polymer chains being obtained by copolymerization and hydrogenation of an aromatic vinyl compound monomer and a conjugated diene monomer, the poly(alkyl (meth)acrylate) (B) having a weight average molecular weight of 200,000 to 600,000, the content (M.sub.A) of the star polymer (A) in the engine oil composition being 0.10 to 2.00 mass % based on the total mass of the engine oil composition, the content (M.sub.B) of the poly(alkyl (meth)acrylate) (B) in the engine oil composition being 0.50 to 6.00 mass % based on the total mass of the engine oil composition, and the ratio M.sub.A/M.sub.B being 0.10 to 1.00. The engine oil composition can significantly improve fuel efficiency, and is suitably used for a diesel engine.

In some embodiments, a lubricating oil includes at least 50 wt % of a base oil, based on total weight of the lubricating oil. The lubricating oil includes at least 0.1 wt % of a polypropylene homopolymer having a racemic dyad content of about 60% to about 99% and a number average molecular weight (by GPC DRI) of about 10,000 g/mol to about 250.000 g/mol, wherein a total amount of the base oil and the polypropylene homopolymer does not exceed 100 wt %.

In some embodiments, a lubricating oil includes at least 50 wt % of a base oil, based on total weight of the lubricating oil. The lubricating oil includes at least 0.1 wt % of a polypropylene homopolymer having a racemic dyad content of about 60% to about 99% and a number average molecular weight (by GPC DRI) of about 10,000 g/mol to about 250.000 g/mol, wherein a total amount of the base oil and the polypropylene homopolymer does not exceed 100 wt %.

Provided is a lubricating oil composition for a shock absorber, which realizes excellent riding comfort in low-temperature and high-temperature environments and can suppress worsening of riding comfort with time, which is caused by evaporation and shearing of the lubricating oil. The lubricating oil composition for a shock absorber contains (A) a base oil having a pour point of lower than 40 C. and a kinematic viscosity at 80 C. of from 2.0 to 2.7 mm.sup.2/s, (B-1) from 1 to 15% by mass of a polymethacrylate having a weight-average molecular weight of from 10,000 to less than 100,000, and (B-2) from 0.1 to 5% by mass of a polymethacrylate having a weight-average molecular weight of from 100,000 to 200,000.

The disclosed technology relates to a heat transfer fluid and a heat transfer system and heat transfer method employing the heat transfer fluid. In particular, the technology relates to a heat transfer fluid with low electrical conductivity, low flammability, and low freeze point that provides excellent peak temperature reduction in a heat transfer system, such as that for cooling a power system of an electric vehicle or a computer server.