Abstract: The compatibility with nitrile ester seals of lubricating compositions containing active sulphur-containing additives may be enhanced bt treating the additives, or concentrates containing them, or the composition themselves, with one or more olefinically unsaturated compounds selected from:(a) acyclic compounds having at least two double bonds with adjacent double bonds separated by two saturated carbon atoms;(b) compounds containing an acyclic ring, which ring contains at least, eight carbon atoms and at least two double bonds, each double bond being separated from the closest adjacent double bond(s) by two saturated carbon atoms; and(c) compounds containing a saturated alicyclic ring and at least one exocyclic double bond.