The invention relates to a liquid composition comprising a major amount of an oil and a minor amount of an additive composition, wherein the additive composition comprises BHQ and N,N'-disalicylidene propylene diamine, and wherein at least 2% by weight of the oil is derived from a plant or animal material. The invention also relates to a method of preventing or retarding the oxidation of the liquid composition and the use of the additive to prevent or retard the oxidation of the liquid composition.