| 摘要 |
PROBLEM TO BE SOLVED: To obtain the subject composition useful for an internal combustion engine, etc., capable of exhibiting high oxidation stability, usable under severe conditions, by mixing a base oil comprising a specific saturated hydrocarbon component and an aromatic hydrocarbon component with a prescribed amount of a sulfur-containing antioxidant. SOLUTION: This composition is obtained by formulating (A) a base oil comprising (A1 ) 70-97 (mass)% of a saturated hydrocarbon component and (A2 ) 2-30 wt.% of an aromatic hydrocarbon component, has <=1 (mass)% of resin content, a value of the equation: kp<1> [RH]<1> kp<1> is a rate constant (M<-1> S<-1> ) of hydrogen drawing reaction by t-butyl peroxyradical (Z) of the component A1 at 40 deg.C; [RH]<1> is an average number of mols of the component A1 of A1 1L} of <=0.3 and a value of kp<2> [RH]<2> kp<2> is a rate constant (M<-1> S<-1> ) of hydrogen drawing reaction by Z of the component A1 at 40 deg.C; [RH]<2> is an average number of mols of the component A2 of A2 1L} of 1-20 with (B) 0.01-10 pts.wt. of a sulfur-containing antioxidant such as a compound of the formula (R<1> to R<4> are each a 1-18C hydrocarbon group). |
