Lubricant composition

A lubricating oil composition comprising:

• a base oil,
• a substituted hydroxy aromatic carboxylic acid ester derivative represented by at least one of formula (I) and formula (II) in an amount of from 1 mass % to 7 mass % on the basis of a total amount of the composition, and
• a heterocyclic compound represented by formula (III) or (IV) blended therein in an amount of from 0.05 mass % to 3 mass % on the basis of a total amount of the composition;
• wherein:
• a phosphorus content in the lubricating composition is 0.06 mass % or less on the basis of a total amount of the composition;
• a sulfated ash content in the lubricating composition is 0.5 mass % or less on the basis of a total amount of the composition;
• in formula I:
• each of x and y is an integer satisfying 1≦x≦3 and 1≦y≦3, respectively,
• each of R1 and R2 represents an alkyl group having 9 to 20 carbon atoms and may be the same as or different from each other, and
• in the case of 2≦x≦3 and 2≦y≦3, plural R1s may be the same as or different from each other and plural R2s may be the same as or different from each other;
• in the formula II:
• each of m, n, o, and p is an integer satisfying 1≦m≦2, 0≦n≦2, 2≦(m+n)≦4, 1≦o≦3, and 1≦p≦3, respectively,
• each of R1 and R2 represents an alkyl group having 9 to 20 carbon atoms and may be the same as or different from each other, and
• in the case of 2≦o≦3 and 2≦p≦3, plural R1s may be the same as or different from each other and plural R2s may be the same as or different from each other;
• and
• in formula (III) and formula (IV):
• R3 represents a linear or branched alkyl group having 7 to 17 carbon atoms,
• n is 6 to 18,
• each R4 is independently selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a —COR5 group, and an —OR6 group,
• R5 is an alkyl group having 1 to 17 carbon atoms, and
• R6 is an alkyl group having 1 to 18 carbon atoms,
• wherein the lubricating oil composition has a residual percentage of base number of from 36 to 47% determined as Residual percentage of base number (%)=[{Base number after the hot tube test (by the hydrochloric acid method)}/{Base number of new oil (by the hydrochloric acid method)}]×100.