Lubricant composition of improved antioxidant properties

In a composition of matter of improved antioxidant properties comprising from 0 to 45 weight percent of (1) an oil of lubricating viscosity, and (2) from 10 to 90 weight percent of an oil-soluble antioxidant selected from (i) sterically hindered phenolic compounds wherein the sterically hindering groups are alkyl groups, said sterically hindered phenolic compounds having from 10 to 40 carbon atoms, (ii) aromatic amine compounds having from 12 to 40 carbons and from 1 to 3 amine nitrogens, (iii) sulfurized organic compounds containing 3 to 40 weight percent sulfur present as thio or polythio linkages or mixtures thereof, and (iv) mixtures thereof, the improvement comprising adding thereto (3) from 5 to 50 weight percent of a bisphosphoramide prepared by reacting (a) phosphorus oxychloride, (b) a hydrocarbyl polyamine having from 2 to 7 amine nitrogens and from 2 to 20 carbons and having at least 1 primary amino group, and (c) a hydrocarbyl monoamine having from 2 to 40 carbons, wherein the molar ratio of monoamine and polyamine to molar part of phosphorus oxychloride is from 1 to 3 molar parts of monoamine and 0.4 to 0.6 molar parts of polyamine per molar part of phosphorus oxychoride, the ratio of said anti-oxidant to said bisphosphoramide being 0.1 to 20:1.