Compositions useful as lubricants comprising a major proportion of an oleaginous liquid of lubricating viscosity and an additive mixture of(a) a zirconium salt of a carboxylic acid or mixture of carboxylic acids, and(b) at least one oil-soluble sulfur-containing extreme pressure agent containing up to about 25% combined sulfurAre described. Such compositions are useful as extreme pressure lubricants such as gear lubricants adapted for heavy duty service.