Friction modifiers for engine oil composition

A lubricating oil composition which comprises an oil of lubricating viscosity and, as a friction modifying fuel economy additive, an effective amount of ester formed as the reaction product of (i) a tertiary amine of the formula R1R2R3N wherein R1, R2 and R3 represent aliphatic hydrocarbyl groups having 1 to 6 carbon atoms, at least one of R1, R2 and R3 having a hydroxyl group with (ii) a saturated or unsaturated fatty acid having 10 to 30 carbon atoms wherein the ester is a mixture of mono-, di and tri-esters, the mixture comprising about 30–60 wt. % diester, 10–40 wt. % monoester and 10–40 wt. % triester and wherein each of R1, R2 and R3 is a C2–C4 hydroxyalkyl group.