Lubricant

A lubricant comprising a diamide derivative of the formula ##STR4## wherein R.sub.5 represents a C.sub.14 -C.sub.18 alkyl or alkenyl radical and a as a base lubricant an imide compound selected from the group consisting of imide compounds having the following formulas ##STR5## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 represent a C.sub.8 -C.sub.18 saturated or unsaturated hydrocarbon radical, said imide compound being obtained by the reaction of a dibasic acid selected from the group consisting of succinic acid, maleic acid, glutaric acid and phthalic acid or the anhydride thereof with at least one primary amine having a corresponding C.sub.8 -C.sub.18 hydrocarbon radical at 100.degree. to 180.degree. C. under atmospheric pressure in a mole ratio of the dibasic acid to the primary amine of from 1:1 to 1:less than 2.