Abstract: Dispersant/VI improver lubricating oil additives are produced by reacting a star polymer with an alpha, beta unsaturated carboxylic acid or derivative to form an activated star polymer, which is then reacted with (a) at least one compound of general formulaRO(AO).sub.n Hwherein R is a C.sub.4-20 alkyl group, A is an independent moiety of either ethylene or propylene, an n is an integer from 0 to 10, optionally followed by reacting with (b) an alkyl carboxylic acid and/or (c) an alkylamine or alkane polyol, or with the preformed product of reactions (b) and (c), optionally followed by esterifying any residual acid groups with a C.sub.1-6 alkanol.

Abstract: A process for preparing a grafted star polymer which comprises contacting a nitrogen-containing polymerizable organic polar compound with a star polymer (as hereinbefore defined) in the presence of a free radical polymerization initiator and characterized in that the reaction is carried out in a mineral oil solvent and, as coupling inhibitor, either a chain transfer agent, a pi-electron donor, or a comonomer, together with the modified, hydrogenated star polymers thus produced, and their use as luboil additives.

Abstract: Improved dispersant/VI improver luboil additives are produced by reacting a hydrogenated conjugated diene star polymer or block copolymer with an alpha, beta unsaturated carboxylic acid or derivative to form an activated star polymer, which is then reacted with a) an alkyl carboxylic acid and b) an alkylamine or alkane polyol, or with the preformed product of reactants a) and b).