Lubricant composition

A lubricating oil composition, comprising:

• a base oil having a content in a range of 94.00% by mass to 94.88% by mass based on a total amount of the lubricating oil composition;
• a phosphite ester derivative having at least one alkyl group having 1 or more and 20 or less carbon atoms in which one —CH2— group is substituted with a —S— group;
• a thiadiazole derivative;
• and
• a polymethacrylate having a content of 0.10% by mass or less based on the total amount of the lubricating oil composition,
• wherein the phosphite ester derivative includes a compound of formula (A1) and a compound of formula (A2),
• where each of RA11, RA21, and RA22 is independently an alkyl group having 8 carbon atoms, and each of aA11, aA21, and aA22 is independently an integer of 2, the phosphite ester derivative has a content in a range of 0.30% by mass to 1.06% by mass based on the total amount of the lubricating oil composition, and the compound of the formula (A1) has a content in a range of 89% by mass to 90% by mass based on a total amount of the phosphite ester derivative, and the thiadiazole derivative comprises a thiadiazole ring and a side chain attached to the thiadiazole ring and having a branched alkyl group, the thiadiazole derivative includes a compound of formula (B1),
• where each of RB11 and RB12 is independently a —XB41—RB41 group, where XB41 is —S—S—, and RB41 is a branched alkyl group having 9 carbon atoms,
• wherein the compound of the formula (A1) has a content in a range of 0.27% by mass to 0.95% by mass based on the total amount of the lubricating oil composition, and the compound of the formula (A2) has a content in a range of 0.03% by mass to 0.11% by mass based on the total amount of the lubricating oil composition,
• wherein the compound of the formula (B1) has a content of 0.20% by mass to 0.80% by mass based on the total amount of the lubricating oil composition,
• wherein the base oil includes at least one selected from the group consisting of 60N hydrocracked mineral oil, 70N hydrocracked mineral oil, 100N hydrocracked mineral oil and 150N hydrocracked mineral oil,
• wherein the 60N hydrocracked mineral oil has a content in a range of 20% by mass to 75.60% by mass based on the total amount of the lubricating oil composition, the 70N hydrocracked mineral oil has a content in a range of 0% by mass to 1.17% by mass based on the total amount of the lubricating oil composition, the 100N hydrocracked mineral oil has a content in a range of 0% by mass to 74.00% by mass based on the total amount of the lubricating oil composition, and the 150N hydrocracked mineral oil has a content in a range of 0% by mass to 18.50% by mass based on the total amount of the lubricating oil composition.