Crude oil of fuel oil compositions

This patent describes a crude oil composition or a fuel oil composition. It comprises: a major proportion by weight of a crude oil or a liquid hydrocarbon fuel and a minor proportion by weight of a polymer containing more than one amide group. The amide being an amide of a secondary mono amine and wherein the amide group of the polymer contains a hydrogen- and carbon- containing group of at least 14 carbon atoms, provided that if the polymer is derived from the polymerization of an aliphatic olefin and maleic anhydride. The polymer must have both an amide group and an ester group each of which contains a hydrogen- and carbon-containing group of at least 14 carbon atoms.