Ethanol In Your Gasoline Tank: The Pros And Cons

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Biofuel crops (photo: Texas A&M University biofuels research alliance)

Biofuel crops (photo: Texas A&M University biofuels research alliance)

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With flex-fuel cars that can run on E85 ethanol still a minority of the vehicles on sale, you might think ethanol isn't as important as some other future fuels.

But up to 10 percent of every gallon of gasoline you buy today is ethanol, and that proportion may rise to as much as 15 percent if gas stations migrate to so-called blender pumps.

Congress has mandated increasing volumes of ethanol in the U.S. fuel mix, though some analysts say the rules simply can't be met.

So what exactly are the benefits--and the problems--of using ethanol as a vehicle fuel, in whatever proportion?

Click the links to check out the pros and cons of both hybrid vehicles and diesel cars.


There are many reasons to support a move away from fossil fuels, but one of the most compelling is to improve U.S. energy independence.

Though the U.S. has its own reserves of crude oil, large amounts are still bought in from politically unstable regions of the Middle East.

Reducing the use of a fuel that could suddenly dry up through trade restrictions or suddenly cost more is very much a priority, and ethanol--which is mostly produced domestically--is one way of hedging against those threats.

Large swathes of countryside, particularly in the Midwest, are set aside for the corn used as a feedstock for refining ethanol.

As demand increases, that has a positive effect on jobs. More ethanol production in the U.S. means more jobs for U.S. citizens.

Ethanol is also greener than gasoline, because corn and other plants absorb carbon dioxide from the atmosphere as they grow. The fuel still releases CO2 when you burn it, but the net increase is lower.

Potentially, ethanol is also tailor-made for newer, higher-compression engines.

A high compression ratio usually requires higher octane levels in the fuel to prevent pre-ignition, a condition that puts high levels of stress on an engine. Ethanol has a higher octane rating than regular gasoline, so it's suited to these efficient, high-compression designs.

Lastly, using ethanol as a small portion of the gasoline blend offers adaptability. Any car since 1980 has been designed to handle up to 10 percent ethanol in the gasoline, letting you run that percentage of your miles on a domestic fuel rather than irreplaceable fossil fuels.

But to go with the Pros, there are also some Cons (see next page).

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