The Impact of Organomolybdenum Compounds on the Frictional Characteristics of Crankcase Engine Oils

To enhance the “Energy Conserving” (EC) performance of crankcase engine oils, the friction reducing capabilities of several oil-soluble organomolybdenum (OM) compounds were evaluated in formulations containing different base oils and viscosity index improvers (VIIs). Using a Cameron-Plint TE 77 Reciprocating Friction Machine, operating under boundary lubrication conditions, OM additives reduced friction coefficients by almost 80%. Frictional force reductions were sensitive to temperature and the apparent “solvency” of the base oil employed in the formulation. Optimum performance was generally observed in base oils of “poorer” solvent quality (high Viscosity Index or high saturate content) or in conventional mineral oils at temperatures above 100°C.

Fullerene carbon cluster molecules (Buckyballs) were found to be inactive as friction modifiers but they influenced the solvational characteristics of base oils and, subsequently, affected the performance of OM friction modifiers by lowering the onset temperature for friction reduction. The impact of VII type on the frictional performance of engine oils was also studied. Dispersant antioxidant olefin copolymers were found to lower friction coefficients by 10-15% over other VII compositions. Sequence VI Fuel Economy Engine Tests confirmed the EC characteristics of these polymers.