A lubricating oil composition comprising: an oil of lubricating viscosity in a major amount in excess of 50 mass % of the lubricating oil composition; an oil-soluble or oil-dispersible additive component as an additive in a minor amount of 0.1 to 15 mass % of the lubricating oil composition, based on the total mass of the lubricating oil composition, wherein additive component is obtainable by the reaction of a polybutenyl succinic acylating agent derived from a polyalkene having a number average molecular weight (Mn) of from 100 to 5000, with a compound of general Formula I: wherein: each Ar independently represents unsubstituted, except for groups Y and terminal groups, naphthalene; each L independently represents a C 1 to C 6 alkylene linking group; each Y independently represents -OR 1 or a moiety of the formula H(O(CR 2 R 3) n) y O-, wherein: each R 1 independently represents a C 1 to C 10 alkyl group; each R 2 and R 3 independently represents H, or C 1 to C 6 alkyl group; n is 2 to 10; and y is 1 to 30; each a is independently 0 to 3, with the proviso that at least one Ar moiety bears at least one group Y of the formula H(O(CR 2 R 3) n) y O-; and, m is 1 to 100; and, wherein the lubricating oil composition is contaminated with at least 0.3 mass %, based on the total mass of the lubricating oil composition, of biodiesel fuel which is at least one alkyl ester of a C 10 to C 30 long chain fatty acid derived from vegetable oils or animal fats. an oil of lubricating viscosity in a major amount in excess of 50 mass % of the lubricating oil composition; an oil-soluble or oil-dispersible additive component as an additive in a minor amount of 0.1 to 15 mass % of the lubricating oil composition, based on the total mass of the lubricating oil composition, wherein additive component is obtainable by the reaction of a polybutenyl succinic acylating agent derived from a polyalkene having a number average molecular weight (Mn) of from 100 to 5000, with a compound of general Formula I: wherein: each Ar independently represents unsubstituted, except for groups Y and terminal groups, naphthalene; each L independently represents a C 1 to C 6 alkylene linking group; each Y independently represents -OR 1 or a moiety of the formula H(O(CR 2 R 3) n) y O-, wherein: each R 1 independently represents a C 1 to C 10 alkyl group; each R 2 and R 3 independently represents H, or C 1 to C 6 alkyl group; n is 2 to 10; and y is 1 to 30; each a is independently 0 to 3, with the proviso that at least one Ar moiety bears at least one group Y of the formula H(O(CR 2 R 3) n) y O-; and, m is 1 to 100; and, wherein the lubricating oil composition is contaminated with at least 0.3 mass %, based on the total mass of the lubricating oil composition, of biodiesel fuel which is at least one alkyl ester of a C 10 to C 30 long chain fatty acid derived from vegetable oils or animal fats. each Ar independently represents unsubstituted, except for groups Y and terminal groups, naphthalene; each L independently represents a C 1 to C 6 alkylene linking group; each Y independently represents -OR 1 or a moiety of the formula H(O(CR 2 R 3) n) y O-, wherein: each R 1 independently represents a C 1 to C 10 alkyl group; each R 2 and R 3 independently represents H, or C 1 to C 6 alkyl group; n is 2 to 10; and y is 1 to 30; each a is independently 0 to 3, with the proviso that at least one Ar moiety bears at least one group Y of the formula H(O(CR 2 R 3) n) y O-; and, m is 1 to 100; and, wherein the lubricating oil composition is contaminated with at least 0.3 mass %, based on the total mass of the lubricating oil composition, of biodiesel fuel which is at least one alkyl ester of a C 10 to C 30 long chain fatty acid derived from vegetable oils or animal fats.