Friction modification of synthetic gear oils

Gear lubricant compositions having a kinematic viscosity at 100 DEG C in the range of 4 to 32 mm .s (cSt), and comprise (a) a base oil having (i) more than 20% by volume of hydrogenated poly- alpha -olefin oil and (ii) less than 80% by volume of mineral oil or synthetic ester oil or a combination thereof; (b) an amount of an additive package such that the lubricant satisfies or exceeds the specifications for API GL-4 service; and (c) a friction improving amount in the range of 0.01 to 2 wt% based on the total weight of the lubricant of at least one overbased alkaline earth metal sulphurised phenate or salicylate, the lubricant being essentially free of any metal additive component other than said phenate or salicylate, and has on a weight basis a boron content, if any, of not more than 1,000 ppm.