Over the last few years federally-mandated fuel and pollution standards resulted in increasing amounts of ethanol, or corn-based fuel, being added to gasoline around the country. The amount depends upon the refinery, and seller.  Some firms are embracing ethanol more than others, but it's in many blends of gasoline.

The AAA has re-issued a warning that first came out months ago that the latest blend, called E15, could potentially damage or destroy your engine. The E stands for ethanol and the number reflects the amount of it the fuel contains. You may have seen vehicles that run on E85 -- 85 percent ethanol + 15 percent gasoline. But these vehicles were specifically designed for such a mix. E15 contains 15 percent ethanol-based fuel and, according to tests conducted many months ago, was reportedly responsible for corrosion to the fuel system, accelerated engine damage and even false "check-engine" lights on dashboards.

According to AAA Vice-President of Public Affairs Chuck Mai:

'"BMW, Chrysler, Toyota, Nissan and Volkswagen are on record stating that their warranties will not cover fuel-related claims resulting from the use of E15. Several others -- Ford, Honda, Hyundai, Kia. Mazda, Mercedes-Benz and Volvo -- have said that E15 does not comply with their cars' fuel requirements specified in owners manuals, and use of it may void warranties."

AAA also added this information:

Today, only 12 million out of the more than 240 million vehicles on the road today (about 5 percent) are approved to use the 'flex fuel,' with E15 in it.

AAA's new warning came on the heels of the EPA approving the fuel for roll out in a number of cities. AAA believes more testing is needed to determine if changes need to be made to the fuel to address these issues. Consumer Reports are among the critics who point to performance issues and other related mechanical problems that have resulted, especially in slightly older vehicles, from use of ethanol.

So far, E15 has been restricted to a few larger markets and is in very limited use.