Lubricating oils of enhanced oxidation stability containing n-phenyl-naphthyl amines, or substituted derivatives of n-phenyl naphthyl amine and carbodiimide acid scavengers

A lubricating oil composition of enhanced oxidation stability comprising a major amount of a base oil of lubricating viscosity selected from the group consisting of natural mineral oils and synthetic oil and mixtures thereof wherein said natural mineral oils have a saturates content of at least about 92%, and said synthetic oils are selected from the group consisting of polyalpha olefins, gas conversion oils, and phosphate esters and a minor amount of additives comprising carbodiimide and N-phenyl-naphthyl amine or substituted derivative of N-phenyl naphthyl amine, wherein the N-phenyl naphthyl amine or substituted derivative of N-phenyl naphthylamine is of the general formula:

• ##STR3## wherein R.sub.3, R.sub.4 and R.sub.5 are the same or different and are hydrogen, C.sub.1 -C.sub.12 hydrocarbyl group, or C.sub.1 -C.sub.12 hydrocarbyl group containing O, N or S heteroatom or heteroatom moiety containing group selected from the group consisting of carboxyl, hydroxy, carbonyl, ether, ester, thioether, amine and mixtures thereof wherein the heteroatom moiety containing group is substituted onto the C.sub.1 -C.sub.12 hydrocarbyl backbone, or the heteroatom constitutes part of the hydrocarbyl backbone and x, y and z are the same or different and are 1 to up to the unsatisfied valence of the respective phenyl and naphthyl moiety.