A lubricating oil additive composition including: (i) at least one first amide compound, and/or a salt thereof, the at least one first amide compound being a monoamide of at least one fatty acid (a1), and at least one amine compound (a2), the amine compound (a2) being an oligomer of at least one alkanolamine (a3) represented by the general formula (1); and (ii) at least one second amide compound having a structure such that an amino group and at least one hydroxy group of the alkanolamine (a3) are acylated with the fatty acid (a1): ##STR00001##
in the formula, n is 1 or 2; R.sup.1 is C1-4 linear chain alkylene or C3-10 branched chain alkylene having a main chain, the main chain having a carbon number of 2; and when n is 2, a plurality of R.sup.1's may be the same, and may be different from each other.