Abstract: Lubricating and functional fluid compositions are described which comprise at least one oil of lubricating viscosity and an extreme-pressure and friction-modifying amount of(A) at least one phosphite ester characterized by the formula ##STR1## wherein R.sup.1 is a straight-chain hydrocarbyl group and R.sup.2 is a branched-chain hydrocarbyl group. The invention also relates to compositions which comprise the combination of such phosphite esters as represented by Formula I and various sulfur-containing compositions. The compositions comprising said combinations also are useful in lubricating and functional fluid compositions including lubricating oils and greases. Aqueous systems containing the phosphite esters represented by Formula I as well as combinations of phosphite esters with sulfur-containing compositions also are described.

Abstract: Reaction products of 5-norbornene-2,3-dicarboxylic anhydride O,O-dialkyldithiophosphate adduct of the formula ##STR1## have been found to be beneficial additives for functional fluids used in the machinery of motorized vehicles. These additives are effective extreme pressure agents and antiwear agents as well as antioxidants for use in such functional fluids as lubricating oils including automatic transmission fluids and hydraulic fluids.