A lubricant composition for a high load carrying oil comprises a synergistic mixture of a neutral alkyl phosphorus compound and a sulphur carrier. The neutral alkyl phosphorus compound is selected from neutral alkyl and alkoxyalkyl phosphates, phosphonates, phosphinates and phosphites. Preferred neutral alkyl phosphorus compounds are triisobutyl phosphate, tributoxyethyl phosphate and dioctyl octyl phosphonate. Preferred sulphur carriers are sulphurised fatty acid esters and dialkyl polysulphides. High load carrying oils containing the lubricant composition of the invention include metal working fluids, gear oils, extreme pressure turbine oils and hydraulic oils.