Consumer Reports magazine put a 2007 Chevrolet Tahoe flexible-fuel vehicle running on E85 (an 85 percent ethanol/15 percent gasoline mix) through a battery of tests, and concludes it will cost consumers more than a gasoline burner. A chief limitation comes from ethanol’s lower energy content, which means that vehicles running on ethanol will have poorer fuel economy. According to the report, “in highway driving, gas mileage decreased from 21 to 15 mpg; in city driving, it dropped from 9 to 7 mpg.” They note that part of E85’s problem arises from use of an engine designed to work most efficiently with gasoline — an engine designed exclusively for ethanol would perform better. Not all results favored gasoline: Consumer Reports found a significant decrease in smog-building nitrongen oxide emissions when using E85.
Only a portion of Consumer Reports ethanol analysis is available online to non-subscribers, more appears to be available in the October 2006 print edition.