Lubricating oil composition

A lubricating oil composition for an automatic transmission or a continuously variable transmission which comprises (a) a base oil comprising at least one selected from the group consisting of mineral oils and synthetic oils, (b) a copolymer having a repeating unit (I) represented by the formula (I) ##STR15## wherein R.sup.1 is hydrogen or an alkyl group having 1 to 6 carbon atoms;

• A is a group of the following formula (I-1);
• n is an integer of 1 to 8;
• ##STR16## wherein each of R.sup.2 and R.sup.3 is independently hydrogen or an alkyl group having 1 to 20 carbon atoms;
• and R.sup.1 and A may be the same or different every repeating unit,
• and a repeating unit (II) represented by the formula (II) ##STR17## wherein R.sup.4 is hydrogen or an alkyl group having 1 to 6 carbon atoms;
• R.sup.5 is an alkyl group having 1 to 24 carbon atoms, and R.sup.4 and R.sup.5 may be the same or different every repeating unit, (c) an amine-based antioxidant, a (d) thiadiazole compound which is a 1,3,4-thiadiazole compound, a 1,2,4-thiadiazole compound or a mixture of these thiadiazole compounds represented by the formula (VII) and (VIII) ##STR18## wherein each of R.sup.9 and R.sup.10 is independently hydrogen, a hydrocarbon group having 1 to 30 carbon atoms, or a group represented by the formula (IX), (X) or (XI) ##STR19## wherein each of R.sup.11, R.sup.12, R.sup.13 and R.sup.14 is independently hydrogen or a hydrocarbon group having 1 to 30 carbon atoms, and (e) a phosphorous acid ester or an amine salt of a phosphorous acid ester.