Patent ID: 8435932

Claim:
A method of lubricating an axle gear comprising supplying to the axle gear a lubricating composition comprising an oil of lubricating viscosity, a thiadiazole-functionalised dispersant and a polysulphide, wherein the polysulphide comprises at least 20 wt % of tri- or higher sulphides, and wherein the thiadiazole-functionalised dispersant is prepared by heating together ingredients comprising: (i) a dispersant substrate; (ii) a thiadiazole compound; (iii) a dicarboxylic acid of an aromatic compound selected from the group consisting of 1,3 diacids and 1,4 diacids, (iv) optionally a borating agent; and (v) optionally a phosphorus acid compound, said heating being sufficient to provide a product of (i), (ii), (iii) and optionally (iv) and optionally (v), which is soluble in an oil of lubricating viscosity.