[MagicRat]

Ethanol has fewer BTU's per volume, hence mileage is a little less.

I'm pretty sure ethanol burns with no carbon or soot, so there will be no carbon build up in the engine, and the engine oil will stay a bit cleaner. Carbon build-up can be a bit of a problem with gasoline burning engines when they are operated at low revs and light throttle for long periods of time.

Ethanol burns much more cleanly, for lower emissions of some pollutants, although this is not much of a problem with Gasoline, given modern pollution controls.

But generally, the BIG advantage of ethanol is that it is theoretically carbon - neutral. The plants (mostly corn) that supply the material for making ethanol suck carbon dioxide from the air to grow. Some of this carbon is released back into the air when ethanol is burned, unlike gasoline, where the carbon released had been sequestered for millions of years.

Therefore, ethanol has a lower impact on the environment. But this is not so simple. Farm machinery used to grow the corn burn diesel, thus are releasing sequestered carbon anyways. So even ethanol negatively impacts the environment.