Lubricant formulation comprising friction modifier additive

The invention provides a lubricant formulation comprising: (a) a base oil selected from API Group I to V oils and mixtures thereof; (b) 0.01 to 10 wt % on the basis of the total weight of the lubricant formulation of a friction modifier additive; and (c) other lubricant formulation additives. The friction modifier additive has a hydroxyl value in the range from 10 to 300 mg KOH/g and is the reaction product of reactants comprising: i) a dimer fatty acid; ii) a polyol; iii) optionally, a C2 to C12 dicarboxylic acid or diol; and iv) optionally, a C1 to C10 mono-carboxylic acid or mono-alcohol. The invention also provides a method of lubricating an internal combustion engine comprising a crankcase and a wet clutch and the use of a friction modifier additive.