Combining a metal based friction modifier, such as a molybdenum dialkyldithiocarbamate, and certain esters of hydroxy carboxylic acids, such as short chain alkyl esters of citric or tartaric acid, e.g., tributyl citrate, has a synergistic effect on lowering the friction coefficient of lubricating oils allowing one to reduce the amount of metal based friction modifier needed to adequately formulate a lubricant with low friction characteristics.