PURPOSE: To use an oil additive composition in an engine and a transmission by mixing a metal salt of phenol sulfide, a metal salt of dithiophophoric acid, an ashless dispersant, a metal salt of sufonic acid detergent and a Mn salt of carboxylic acid to lubricating viscous oil.

CONSTITUTION: A lubricant composition usable in a diesel engine and a transmission is obtained by mixing small quantities of (A), (B), (C), (D) and (E) additives to lubricating viscous oil is a neutral or basic Ca salt or Mg salt of phenol sulfide shown by formula I (R1-2 are each H, a 1-20C alkyl), (B) is a dithiophophate shown by formula II ((R3-4 are each a 3-18C alkyl, aryl, 1-18C alkyl-substituted aryl L; M is a first to second group metal, Sn, Mo, Mn, Cu, Zn) (C) is an ashless dispersant selected from a reactant of a substituted succinc acid acylating agent with amines, a Mannich dispersant, an ester dispersant and their mixtures and, (E) is a Mn salt of carboxylic acid.