A polymeric lubricant additive that behaves as a viscosity index improver and imparts enhanced anti-oxidancy, dispersancy, and anti-wear properties to said lubricant oil has been prepared. The polymeric substrate is a random co- or terpolymer of ethylene propylene and a third monomer; or a block terpolymer of styrene-(ethylenebutylene)-styrene where hydrogenation has removed aliphatic unsaturation. Ethylenically unsaturated carboxylic acid or acid anhydride is grafted to these aforementioned substrates and imidized with amino-thiadiazole of the formula: ##STR1## wherein R.sub.1 is H.sub.2 or a (C.sub.1 -C.sub.10) alkyl radical selected from the group consisting of a alkyl, alkenyl, alkoxyl, aralkyl, alkaryl, hydroxyalkyl and aminoalkyl, to produce said polymeric lubricant additive.