Patent ID: 8592356

Claim:
A lubricating oil composition, comprising: (L) a lubricating base oil; (A) component (A), which is at least one of (a1) a disulfide compound of formula (1) R 1 OOC-A 1 -S—S-A 2 -COOR 2 (1), and (a2) a disulfide compound of formula (2) R 7 OOC—CR 9 R 10 —CR 11 (COOR 8 )—S—S—CR 16 (COOR 13 )—CR 14 R 15 —COOR 12 (2) wherein A 1 and A 2 are independently a group represented by CR 3 R 4 or a group presented by CR 3 R 4 —CR 5 R 6 , in which R 3 to R 6 are independently a hydrogen atom or a hydrocarbyl group comprising 1 to 20 carbon atoms, R 1 , R 2 , R 7 , R 8 , R 12 , and R 13 are independently a hydrocarbyl group comprising 1 to 30 carbon atoms, wherein the hydrocarbyl group optionally comprises an oxygen atom, a sulfur atom, or a nitrogen atom, and R 9 to R 11 and R 14 to R 16 are independently a hydrogen atom or a hydrocarbyl group comprising 1 to 5 carbon atoms; (B) component (B), which is a boron-free ashless dispersant comprising, in its side chain, (b1) an alkyl group having a number average molecular weight of 950 to 3000; or (b2) an alkenyl group having a number average molecular weight of 950 to 3000; and (C) component (C), which is a boron-containing ashless dispersant comprising, in its side chain, (c1) an alkyl group having a number average molecular weight of 950 to 4000; or (c2) an alkenyl group having a number average molecular weight of 950 to 4000, wherein the lubricating base oil (L) has a % CA of 3 or less, wherein the lubricating base oil (L) has a sulfur content of 50 mass ppm or less, wherein a content of the component (A) is 0.01 to 0.5 mass % of a total amount of the composition based on sulfur, wherein the composition comprises substantially no metal base detergent, and wherein the composition has a phosphorus content of 0.1 mass % or less, based on the total amount of the composition wherein a nitrogen content in the component (B) is 50 to 4000 ppm by mass, based on the total amount of the lubricating oil composition, and wherein a boron content in the component (C) is 50 to 3000 ppm by mass, based on the total amount of the lubricating oil composition.