Abstract: A lubricating oil composition suitable for use in automative transmissions of an automatic type is disclosed. The oil, mineral or synthetic, is combined with specified amounts of C.sub.2 -C.sub.10 monoolefin polymers and methacrylic acid ester copolymers of C.sub.1 -C.sub.18 saturated aliphatic monovalent alcohols, whereby viscosity/temperature characteristics and shear stability in particular are greatly improved.

Abstract: In a central system fluid composition comprising (1) 70 to 95% by weight of a hydrocarbon base oil and (2) 5 to 30% by weight of a viscosity index improver, the improvement wherein said hydrocarbon base oil (1) comprises (a) 25% by weight to less than 50% by weight, based on the weight of the hydrocarbon base oil (1), of an oligomer of 1-decene having an average molecular weight of 200 to 600 and (b) more than 50% by weight to 75% by weight of a petroleum lubricating oil fraction, and said viscosity index improver (2) is a polymethacrylate having a viscosity average molecular weight of 10,000 to 700,000 obtained by polymerizing at least one ester of a saturated monohydric aliphatic alcohol having 1 to 18 carbon atoms with methacrylic acid.

Abstract: A compressor oil composition comprising a major proportion of a lubrication base oil, and a minor proportion of (a) an aromatic amine, (b) an alkylphenol and (c) a triester of dithiophosphoric acid as essential ingredients.

Abstract: A central system fluid composition composed of 5-30% by weight of a viscosity index improver, up to 10% by weight of another additive, and the balance being a hydrocarbon-type base oil, which is characterized in that the hydrocarbon-type base oil is composed of 50-100% by weight, based on its total weight, of at least one chief base oil component selected from the group consisting ofA. polybutenes with an average molecular weight of 100 - 500,B. homo- or copolymers with an average molecular weight of 100 to 500 of at least one .alpha.-olefin containing 2-12 carbons, excepting butenes, andC. hydrogenation products boiling at 250.degree.-380.degree. C of high aromatic components which are obtained by cracking petroleum oils,And 0-50% by weight, based on its total weight, of a mineral oil; and that the viscosity index improver is composed of at least one component selected from the group consisting of1.