Abstract: A lubricating oil composition is herein disclosed which comprises (a) a base oil comprising a mineral oil, a synthetic oil or both the oils, (b) a copolymer having repeating units of the formulae (I) and (II) ##STR1## (c) an amine-based antioxidant, and if necessary, (d) a thiadiazole compound. The repeating unit of the formula (I) is derived from a monomer such as dimethylamino methacrylate. The repeating unit of the formula (II) is derived from a monomer such as a methacrylate of a long-chain alcohol. R.sup.1 and A may be the same or different every repeating unit. This lubricating oil composition is minimized in change with the lapse of time in frictional characteristics (shift shock in an automatic transmission or the like) and is excellent in oxidation stability.