Study Says No Mileage Loss From Ethanol

Despite containing two-thirds of gasoline's energy content in Btu per gallon, ethanol does not lower vehicle miles per gallon when added to gasoline in blends of 20–30% ethanol, says a report by the Minnesota Center for Automotive Research at Minnesota State University, Mankato. Funded by the American Coalition for Ethanol and the Department of Energy, the study compared highway mpg of four 2007 vehicles, three intended to run on gasoline and one a flex-fuel car designed to operate on E85, a mix of 85% ethanol and 15% gasoline. The center's study measured mileage in lab and road conditions while varying ethanol fuel content from zero to 85% ethanol, center Director Bruce E. Jones tells C&EN. Researchers found the regular cars' mileage peaked between 20 and 30% ethanol and was identical to the rate at 100% gasoline. For the flex-fuel car, mileage at a 20% ethanol blend was 15% better than with pure gasoline. Jones urges more research to determine why mileage did not drop as expected due to ethanol's lower Btu value, but he conjectured that the efficiency gains may be attributable to the ability of modern computerized engines to make internal adjustments in timing and burn rate to take advantage of ethanol's characteristics, such as higher oxygen content and octane rating.