Abstract: A process for preparing sulfurized oxymolybdenum organophosphorodithio compounds is described which includes the steps of (A) reacting at reflux in an inert solvent for at least one hour (1) an oxide of molybdenum, (2) a sulfurizing compound selected from the group consisting of sodium hydrosulfide and sodium monosulfide, and (3) a dialkylphosphorodithioic acid, and then (B) recovering the reaction product. Certain of these compounds have fuel efficient characteristics, as well as extreme pressure (E.P.) performance when blended into mineral oils, greases or synthetic lubricating fluids.