The present invention is directed to a crankcase lubricating oil composition for protection of silver bearings in locomotive diesel engines comprising (A) a major amount of an oil of lubricating viscosity, and (B) a silver wear protection additive composition, and (C) one or more detergents. The silver wear protection additive composition of the present invention comprises a mixture of (i) a hydrocarbylamine salt of a di-alkyl di-thiophosphoric acid and (ii) a hydrocarbylamine salt of an alkyl acid phosphate.