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

Claim 1

A mineral lubricating oil composition containing (a) a predominant proportion by weight of mineral lubricating oil, (b) from 0.05 to 2.5% by weight, based on the mineral lubricating oil, of a pour point depressant based on an alkyl acrylate or alkyl methacrylate polymer and (c) from 0.5 to 6% by weight, based on the mineral lubricating oil, of a selectively hydrogenated, random butadiene-styrene copolymer comprising from 35 to 45% by weight of styrene units and from 65 to 55% by weight of hydrogenated butadiene units, which copolymer, prior to hydrogenation, has a 1,2-vinyl content of the polymerized butadiene units of from 23 to 40% by weight, based on copolymerized butadiene units, and which has a 13 C-NMR spectrum in which the ratio of the sum of the intensities of the signals of the CH 2 groups in the β-position and the CH 2 groups of the ethyl branches, ΣCH 2 (β + ethyl), to the sum of the intensities of the signals of the γ-CH 2 and δ-CH 2 carbon atoms and CH 2 carbon atoms more remote from the branch points, ΣCH 2 (γ, δ and more remote), is from 1:1 to 1:1.4, and has an IR spectrum in which the ratio of the extinctions, E, of the styrene bands at 1,180 cm -1 and 1,150 cm -1 , E(1,180)/E(1,150), is from 0.6 to 0.73 and the ratio of the extinctions, E, of the styrene bands at 1,190 cm -1 and 1,180 cm -1 , E(1,190)/E(1,180), is from 0.15 to 0.22, and in which the content of olefinic double bonds has been reduced to a residual proportion of less than 5% as a result of the selective hydrogenation.