Automakers have fired the latest salvo in the ongoing battle against ethanol blends in gasoline, saying it can damage engine components.

That's despite several manufacturers approving it for use in their newest vehicles--adding to the confusion over ethanol in pump gasoline.

According to The Detroit News, the debate once again centers around E15, a gasoline blend containing 15 percent ethanol.

E15 is--as the name suggests--five percent higher in ethanol than the E10 fuel sold in nearly all of the nation's 180,000 gas pumps. The Environmental Protection Agency has approved the fuel for use in vehicles from 2001 and newer.

Ethanol does have several advantages. Energy content isn't one of them--meaning fuel economy on E15 will be a little worse than it is on E10--but that's mitigated by the lower pump cost, roughly 10 to 15 cents per gallon cheaper than E10.

The fuel also has a lower carbon footprint than gasoline, because it's produced from corn, and like any plant corn absorbs CO2 from the atmosphere. And because you can grow it anywhere--specifically, the U.S.--it reduces the need for imported oil and keeps more money in the country. Higher blends in gasoline equal more energy independence.

If only it was all so simple. Automakers say that while they support renewable fuels, the EPA hasn't considered the potential damage higher ethanol blends can do to engine components.

Rubber, plastic, metal and other materials are at risk of degradation with higher blends, particularly in older vehicles not specifically designed for high proportions of ethanol. Volkswagen actually approves E15 for its 2014-and-on model year vehicles, while General Motors and Ford both allow its use in newer vehicles.

Conversely, these companies--plus Chrysler, Toyota and others--are part of the Alliance of Automobile Manufacturers that tried to take the case to the Supreme Court. They say the EPA's decision to approve E15 was rushed, and could have consequences for vehicle life.

The American Automobile Association has also joined the fight, asking the EPA to lower the amount of ethanol blended into gasoline.

On the other side, the Renewable Fuels Association says there's simply a lack of evidence to suggest E15 can damage vehicles--citing more than 40 million cumulative miles of E15 driving with no reported issues.

For consumers, it sends out a confusing message:

Is ethanol going to degrade our engines, or not? Is the problem so minuscule that the car itself will be long gone before any damage causes noticeable problems? And if automakers are approving E15 for use in their cars, why are they also railing against its use in general?


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