Two types of alcohol, ethanol and methanol, are used as alternative fuels in flexible fuel vehicles (FFVs), whose gasoline engines have undergone minor modifications. A high-octane renewable liquid fuel, ethanol is made from corn or other grains, or even from biomass waste. Methanol, a liquid fuel made most often from natural gas (though sometimes from coal or biomass), produces about half the smog-forming emissions of gasoline in a comparable vehicle. Both of these alcohol fuels contain less energy content than gasoline, a situation that results in a shorter driving range. However, manufacturers often equip their FFVs with larger fuel tanks to offset this.

As motor fuels, ethanol and methanol typically are mixed with 15 percent gasoline, creating M85 and E85. The addition of this relatively small percentage of gasoline overcomes cold-starting issues faced by alcohol and also enhances safety, since 100 percent alcohol burns with an invisible flame. The addition of gasoline remedies this danger.

Both ethanol and methanol have been used in FFVs, which are equipped to run on any mixture of alcohol fuel and gasoline in the same tank. However, while M85 FFVs were popular in the mid-1990s and manufactured in small numbers by nearly a dozen automakers, these have fallen by the wayside as interest in methanol diminished. Now, a growing number of E85 FFV models are being offered by select automakers.

You'll find E85 vehicles offered in the most popular segments, from pickups and SUVs to sedans and minivans. It should be noted that these models are available as FFVs only with certain engines.

It's estimated that more than two million E85 FFVs are on U.S. roads. Offsetting this is that there are less than 3,000 ethanol fueling stations in the country, which means most of these vehicles are running on gasoline. That could change in a big way if attention is paid to expanding the ethanol refueling infrastructure and making best use of the alternative fuel vehicles already on the highway.