Lubricating oil compositions containing alkyl acrylate or methacrylate polymers and copolymers of styrene and conjugated diene

摘要

Mineral lubricating oil compositions which contain a predominant proportion of a mineral lubricating oil together with a pour point depressant based on alkyl acrylate or alkyl methacrylate polymers and a viscosity index (VI) improver comprising a special selectively hydrogenated copolymer of styrene and a conjugated diene. The VI improver employed is a selectively hydrogenated, random butadiene-styrene copolymer containing from 35 to 45% by weight of styrene and possessing a particular structure and distribution of the monomers. The compositions exhibit high stability to shear and may therefore in particular be used for lubricating I.C. engines or gearboxes.