A copolymer comprising units of an unsaturated dicarboxylic monomer and an ethylene .alpha.-olefin macromer is disclosed. The macromer is an unsaturated ethylene .alpha.-olefin polymer comprising units of from ethylene and at least one .alpha.-olefin represented by the formula CH.sub.2 .dbd.CHR.sup.a, wherein R.sup.a is a C.sub.1 to C.sub.18 linear alkyl group or a C.sub.3 to C.sub.18 branched alkyl group; the ethylene .alpha.-olefin polymer has a number average molecular weight of from about 500 to about 100,000; and at least about 30% of the unsaturation in the ethylene .alpha.-olefin polymer is terminal vinylidene. The copolymer has a carbon-carbon backbone and contains succinic groups and hydrocarbyl groups. The copolymer can be derivatized by reaction with nucleophilic reactants including monoamines, polyamines, monoalcohols, polyols, amino alcohols, reactant metal compounds and mixtures thereof. The derivatized copolymers can be post-treated (e.g., borated) with one or more post-treating agents (e.g., boric acid). The copolymer, its derivatives, and post-treated derivatives are useful as additives (e.g., dispersants and viscosity index improvers) in fuels and in lubricating oils.