Chances are you don't pay too much attention to the stickers on the gas station pump when you fill up your car except perhaps the one associated with the octane rating you prefer. After all, the worst that could happen are some relatively small differences in performance, right? Not so, if you accidentally put E15, a blend of 15% ethanol and 85% gasoline, in the majority of the cars on the road today.
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Ethanol has long been mixed with gasoline in small quantities, but last year the Environmental Protection Agency approved the sale of E15 gasoline and it has been springing up at gas stations slowly and labels stating so should be on their pumps. Ethanol labels designating use of up to 10%, or so-called E10, have been common for years and aren't a cause for concern by consumers since E10 is safe in all cars. By contrast, a large warning label and a distinctive green pump handle is used to warn consumers of a pump that dispenses diesel fuel, which will cause major damage if used in a gasoline engine. Many groups, including AAA, are concerned that consumers don't realize that using E15 could cause damage to their cars and potentially void the warranty.
About 12 million of the 240 million cars and light-duty trucks on the road currently have been approved by automakers to use E15 gasoline, according to research by AAA. Cars approved to use E15 include all cars designated as "flex fuel," which means they can run on up to 85% ethanol as well as traditional gasoline; 2013 model-year Fords, 2012 model-year and newer cars from GM, and 2001 model-year and newer Porsches. These approvals extend only to cars, light-duty trucks and medium-duty passenger vehicles such as SUVs.
Five auto manufacturers -- BMW, Chrysler, Nissan, Toyota and Volkswagen -- have said they will not honor any fuel-related warranty claims on cars that use E15 gasoline. Eight automakers -- Ford, GM, Honda, Hyundai, Kia, Mazda, Mercedes-Benz and Volvo -- have said that if the use of E15 does not comply with the fuel requirements specified in their owner's manuals, it may void warranty coverage.
Running E15 gasoline in a car that is not approved for it could cause engine problems. Ethanol is known to corrode rubber and some metals and can cause additional moisture in the fuel tank for cars that sit for a while. The EPA feels that all cars that are 2001 model year or newer are built with parts that can withstand a 15% blend of ethanol, but automakers aren't so sure. That's why many have issued warnings or restricted their warranties. Independent research by AAA's auto engineers also finds that using E15 in new and older cars could cause damage to the fuel system, speed up engine wear and cause the "check engine" light to illuminate.
Consumers with cars built by the automakers that have issued warnings against E15 gasoline use as well as consumers who drive cars that are older than 2001 models will want to avoid using the fuel to keep their warranties intact. Fortunately, there should be other choices for fuel, even at the same gas station, making the choice to fuel up with something else relatively easy.
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If you have a car question, email it to us at Driving for Dollars. Read more Driving for Dollars columns and Bankrate auto stories. Follow her on Facebook here or on Twitter @SheDrives.