Novel Test Methods to Optimize Fuel Economy in Passenger Cars Using Organic Friction Modifiers
Fuel economy is overall a very high priority worldwide, but the value of fuel economy can vary to different stakeholders. Many governments set minimum fuel economy standards that force OEMs to make significant investment to achieve. Engine oils and friction modifiers can provide a small but cost-effective contribution to overall fuel economy in cars and trucks. Bench tests that evaluate frictional characteristics often do not correlate well to actual fuel economy benefit. Optimizing a friction modifier to maximize the benefit requires testing the same way that OEMs are required to test fuel economy. Using vehicles on chassis dynamometers, the Highway Test Procedure (HwFET) of the FTP 75 requirement which OEMs follow to quantify their Corporate Average Fuel Economy (CAFE) requirements in North America was modified and used to evaluate individual friction modifier (FM) components and their effects on fuel economy. Since OEM value propositions involve entire fleets, the effect of friction modifiers on fuel economy was tested using several types of vehicles. A new FM additive is shown to demonstrate more than twice the fuel economy benefit compared to glycerol monooleate (GMO), a standard FM used in many engine oils, even at half the treat rate. A Chevrolet 5.7 liter engine on a test stand was also adapted to screen individual components in engine oil and their effects on fuel economy. Results are shown for various components, including an apparent increase in fuel consumption due to the antiwear (AW) component ZDDP.