C.sub.5 -C.sub.9 lactone based adduct materials are made by reacting a C.sub.5 -C.sub.9 lactone with a polyamine, a polyol or an amino alcohol to form a lactone adduct intermediate, and thereafter reacting the intermediate with an aliphatic hydrocarbyl saturated or unsaturated, straight chain or branched chain monocarboxylic or dicarboxylic acylating agent having from about one to about 165 total carbon atoms in said straight or branched chain to insure that the resulting lactone adduct is hydrocarbon soluble. The resulting adduct material are useful per se, as oil soluble dispersant additives, and are useful in fuel and lubricating oil compositions including concentrates containing the additives.