The invention is a method for enhancing and restoring the friction reduction effectiveness of a lubricating oil comprising adding to the lubricating oil a trinuclear molybdenum sulfur compound selected from the group of trinuclear molybdenum compounds preferably those having the formulas Mo.sub.3 S.sub.7 (dtc).sub.4 and Mo.sub.3 S.sub.4 (dtc).sub.4 and mixtures thereof wherein dtc represents independently selected diorganodithiocarbamate ligands containing independently selected organo groups and wherein the ligands have a sufficient number of carbon atoms among all the organo groups of the compound's ligands are present to render the compound soluble or dispersible in the lubricating oil. The oil may be a fresh or used oil. Concentrates of the composition are also included in the invention.