Economic and political factors continue to put pressure on the automotive industry to reduce fuel consumption in vehicles. To increase the fuel efficiency of an engine, engine oil formulations have trended towards lower viscosity and the use of friction modifiers. To improve fuel economy further, the fuel itself can be used to deliver friction modifiers to the piston ring-cylinder wall interface, a location where friction is high and the oil quantity is purposely kept low.
This paper describes the use of the Sequence VI, VI-A, and VI-B lubricant fuel economy tests to demonstrate the fuel consumption improvement from a gasoline friction modifier fuel additive. To capitalize on the dynamometer results, vehicle tests were conducted using several test cycles, engine oils of different viscosity grades and containing a friction modifier, various gasoline friction modifier fuel additive treat rates, and to predict the effect of long term use.
The benefit of the gasoline friction modifier fuel additive was generally found at the higher oil temperature conditions. The fuel economy change was immediately measurable and further gains were seen as the friction modifier fuel additive accumulated in the engine oil and reduced friction in oil-wetted parts of the engine. The use of friction modifiers in engine oil formulations did not negate the fuel additive benefit. This program has shown that using the fuel to supply a friction modifier is a practical method to improve vehicle fuel economy.