An Efficient, High-Precision Vehicle Testing Procedure to Evaluate the Efficacy of Fuel-Borne Friction Modifier Additives

Improved fuel economy is increasingly a key measure of performance in the automotive industry driven by market demands and tighter emissions regulations. Within this environment, one way to improve fuel economy is via fuel additives that deliver friction- reducing components to the piston-cylinder wall interface. Whilst the use of friction modifiers (FMs) in fuel or lubricant additives to achieve fuel economy improvements is not new, demonstrating the efficacy of these FMs in vehicles is challenging and requires statistical design together with carefully controlled test conditions. This paper describes a bespoke, efficient, high-precision vehicle testing procedure designed to evaluate the fuel economy credentials of fuel-borne FMs. By their nature, FMs persist on engine surfaces and so their effects are not immediately reversible upon changing to a non FM-containing fuel (“carryover” effect), therefore requiring careful design of the test programme. The solution presented here comprises a one-day chassis dynamometer test, internally referencing the fuel economy of an FM- containing test fuel to an FM-free reference fuel. When incorporated into a statistically designed test programme, two or more fuels are compared using a chosen test cycle. Comprehensive instrumentation, control and monitoring, integrated vehicle conditioning stages and strict acceptance criteria are major factors in achieving the required precision. This test design is also specially tailored to eliminate the problem of FMs carry-over effects to subsequent tests. Three programmes based on this test procedure have measured statistically significant fuel economy differences between FM-containing fuels and FM-free fuels, thus demonstrating that the required precision has been achieved to evaluate the efficacy of fuel- borne FMs.