A carboxylic derivative composition derived from a carboxylated isobutylene-polyene copolymer having n ranging from about 200 to about 10,000, said copolymer having thereon from about 0.8 to about 7 moles per mole of copolymer of groups derived from at least one .alpha.,.beta.-unsaturated carboxylic acid or reactive equivalent thereof, reacted with at least one of (a) amines characterized by the presence within their structure of at least one condensable H--N< group, (b) alcohols. (c) reactive metals or reactive metal compounds, and (d) a combination of two or more of any of (a) through (c), the components of (d) having been reacted with the carboxylated isobutylene-polyene copolymer simultaneously or sequentially, in any order. Also, a process for preparing carboxylic derivative compositions, additive concentrates and lubricating oil compositions containing the carboxylic derivative compositions and methods for increasing the viscosity index of lubricating oil compositions.