PURPOSE: To provide an N-allyl and/or N-benzyl deriv. of a new p- phenylenediamine useful as an antioxidant for stabilizing a lubricant compsn. against oxidative or thermal degradation.

CONSTITUTION: The compd. of formula [at least one of R1 to R4 is a 3-18C alkenyl, 7-15C alalkyl and the rest are H, a 6-10C aryl which may have 1 to 3 substituents (a 1-20C alkyl, 5-12C cycloalkyl, 7-15C alalkyl, CN, NO2, halogen, etc.); provided that N,N-diallyl-N'-phenyl-p-phenylenediamine is precluded]; for example, N,N,N'-triallyl-N'-phenyl-p-phenylenediamine. The compd. is produced by bringing p-phenylenediamine or n-phenyl-p-phenylenediamine and an alkenyl or aralkyl halide, for example, allyl bromide or benzyl bromide into reaction in the presence of an alkali and quaternary ammonium salt.