Patent ID: 7687444

Claim:
A lubricating oil composition having a total base number (TBN) in the range of 5 to 55 mg KOH/g comprising a major amount of a base oil of lubricating viscosity and a) 0.19 to 2.10 wt %, based on the total amount of the lubricating oil composition, of an overbased calcium carboxylate having a TBN of 100 mg KOH/g or more comprising each of the following compound A and the following compound B, wherein the wt % is expressed in terms of the calcium content, and wherein the overbased calcium carboxylate having a TBN of 100 mg KOH/g or more comprises more than 50 wt % of the following compound A and less than 50 wt % of the following compound B: in which R is an alkyl group having 12 to 28 carbon atoms; b) 0.002 to 0.06 wt %, based on the total amount of the lubricating oil composition, of a bis-succinimide compound, wherein the wt % is expressed in terms of the nitrogen content; and c) 0.007 to 0.15 wt %, based on the total amount of the lubricating oil composition, of a zinc dialkyldithiophosphate having a secondary alkyl group, wherein the wt % is expressed in terms of the phosphorus content.