Patent ID: 7625847

Claim:
A lubricating oil composition comprising a lubricating base oil, (A) an alkali metal or alkaline earth metal salicylate represented by formula (1) below and/or an overbased or basic salt thereof in an amount of 0.005 to 0.4 percent by mass in terms of metal and (B) a phosphorus-containing anti-wear agent in an amount of 0.005 to 0.2 percent by mass in terms of phosphorus and containing sulfur in a total amount of 0.3 percent by mass or less, based on the total mass of the composition, the salicylate being any of salicylates fulfilling at least one of requirements selected from (I) through (IV) or a mixture of the salicylates: wherein R 1 is a hydrocarbon group having 1 to 40 carbon atoms, R 2 is hydrogen or a hydrocarbon group having 1 to 40 carbon atoms, which hydrocarbon groups may contain oxygen or nitrogen, M is an alkali metal or alkaline earth metal, and n is an integer of 1 or 2 depending on the valence of the metal; (I) either one of R 1 or R 2 in formula (1) is a hydrocarbon group having 1 to 9 carbon atoms and the other is a hydrocarbon group having 10 to 40 carbon atoms, and the difference of carbon number between R 1 and R 2 is 10 or more; (II) the component ratio of a salicylate represented by formula (1) wherein R 1 and R 2 are alkyl or alkenyl groups having 10 to 40 carbon atoms is adjusted to be 10 percent by mol or more; (III) the component ratio of a salicylate having one hydrocarbon group having 20 to 40 carbon atoms is 85 percent by mol or more wherein the component ratio of a salicylate represented by formula (1) wherein R 1 is a secondary alkyl group having 20 to 40 carbon atoms and R 2 is hydrogen is adjusted to be 50 percent by mol or more; and (IV) the component ratio of a salicylate having one hydrocarbon group having 10 to 19 carbon atoms is 85 percent by mol or more wherein the component ratio is a salicylate represented by formula (1) wherein R 1 is a secondary alkyl group having 10 to 19 carbon atoms and R 2 is hydrogen is adjusted to be 55 percent by mol or more, wherein Component (B) is a metal salt of a phosphorus compound of formula (3) wherein all of X 4 , X 5 , X 6 , and X 7 are oxygen, and any two of R 6 , R 7 , and R 8 are hydrocarbon groups having 1 to 30 carbon atoms: