On my way to work this morning a pulled up to a stoplight directly behind what I thought was a hybrid Chevrolet Tahoe. Upon closer inspection, I discovered it was instead their flex fuel model. I’d seen the Flex Fuel logo/badge thousands of times on a handful of SUVs but I’d never researched how they compared to other cars in terms of cost and fuel economy. I wasn’t exactly sure what “flex fuel” even meant or how these models differed from conventional  engines and hybrids. Knowing that you can purchase all three options in the 2010 Chevy Tahoe, I decided to take a closer look to compare and contrast the benefits of each.

On the Chevrolet website they pose the question, “Why pump for fuel when you can grow it?”. Chevy has been offering vehicles with engines capable of running on flexible fuels since 2002. Flex-fuel vehicles (FFV) have engines that are specially designed to run on gasoline blended with ethanol. While these engines are theoretically built to run on any combination/blend of gasoline and ethanol, U.S. and European models are optimized for a maximum blend of 15% gas mixed with 85% ethanol. This mixture is better known as E85.

According to my research there are more than 8 million flex fuel vehicles on the roads in the United States today, and roughly 20 million worldwide. What I found most interesting was the fact that flex fuel vehicles actually get worse gas mileage than their traditional gas counterparts. A 2009 ”E85 burning” Tahoe reportedly gets about 25% fewer miles per gallon (11 mpg) than the standard gas model which itself only manages 15 mpg in city driving. The hybrid version gets 21 miles per gallon - nearly double its flex fuel brother. In 2010, all non-hybrid Tahoes are now E85 capable and equipped with a 5.3 liter V8. Starting MSRP is around $38,000.

If E85 fuel reduces your fuel economy by 25%, you’d expect that your cost at the pump would be a similar discount. According to E85prices.com the average spread is currently closer to 20% (the range was 8% to 29%). Other data on that site indicates there are over 2,300 gas stations in the U.S. now offering E85 pumps and that manufacturers spend less than $150 per vehicle to make them capable of running on blended fuel.  GM, Ford and Chrysler have apparently pledged that more than 50% of their cars, trucks and SUVs will be flex fuel capable by 2012.

When comparing the flex fuel capable 2010 Chevrolet Tahoe to the hybrid model, the price difference depends on which trim level you choose. Expect to pay at least $42,000 for an LT model or $51,000 for the more luxurious LTZ (based on 2wd). The hybrid Tahoe falls somewhere in between the LT and LTZ in terms of standard equipment and it starts at $51,000.

According to Wikipedia, using E85 reduces carbon monoxide emissions and provides significant reductions in emissions of many harmful toxins, including benzene, a known human carcinogen. However, E85 also increases emissions of acetaldehyde—a toxic pollutant. No exact emission data is available for the flex fuel Tahoe or the hybrid model for that matter, where a vague 20% improvement is cited. With congress, the EPA and various environmental groups currently debating the future of ethanol blends and their subsidies, this should make for an interesting time in the history of alternative fuel vehicles.