An Investigation into the Effect of Zinc Dithiophosphate on ASTM Sequence VIA Fuel Economy

The International Lubricant Standardization and Approval Committee (ILSAC) GF-2 specification requires Passenger Car Motor Oils to provide enhanced fuel economy in a modern low friction engine as measured by the ASTM Sequence VIA This paper details fundamental studies of the effect of zinc dithiophosphate, both type and level, on fuel economy as measured by this low friction engine The Sequence VIA was found to be very sensitive to both the level of zinc dithiophosphate and the type of alcohol functionality associated with it Increasing the level of zinc dithiophosphate was found to enhance fuel economy as measured by this test particularly in the SAE 10W-30 viscosity grade Secondary zinc dithiophosphates outperformed both primary and aryl types This paper will discuss these findings, as well as report on some fundamental studies using ³¹P-NMR and surface film analysis to determine the fate of zinc dithiophosphate during the course of this test