Critical Oil Physical Properties that Control the Fuel Economy Performance of General Motors Vehicles

The effect of critical physical properties of engine oils on fuel economy performance in General Motors (GM) vehicles has been measured. Reductions in an oil's high temperature high shear viscosity, boundary friction coefficient and pressure-viscosity coefficient were found to equally improve fuel economy. These same oil properties affect fuel economy measured in the Sequence VIA engine test. However, fuel economy performance in GM vehicles is more dependent on an oil's boundary friction coefficient and pressure-viscosity coefficient than that measured in the Sequence VIA engine test. New fuel economy measurement conditions have been proposed for the Sequence VIB engine test. Changes in an oil's boundary friction coefficient were found to have the same effect on fuel economy measured under these new measurement conditions as that measured in GM vehicles.