Hydroxyl terminated polymeric C.sub.5 -C.sub.9 lactone adducts are made by reacting a C.sub.5 -C.sub.9 lactone with the reaction product of a C.sub.2 -C.sub.10 olefin polymer or a halogenated derivative thereof having a number average molecular weight of 300 to about 10,000, with an amine containing from 2 to 60 total carbon atoms and from 1 to 12 nitrogen atoms. The resulting adducts are useful per se as oil soluble dispersant additives. They are also useful in fuel and lubricating oil compositions, as well as in concentrates and additive packages.