CHICAGO — Hoping to capitalize on the buzz over using homegrown alcohol fuel instead of gasoline, auto rivals General Motors and Ford Motor Co. both said yesterday that they're teaming with energy companies on projects that could make so-called E85 a mainstream fuel instead of a boutique rarity.

E85 is a blend that's 85 percent ethanol — alcohol usually made from Midwest corn — and 15 percent gasoline. President Bush said in his State of the Union speech last month that ethanol fuels can help "make our dependence on Middle Eastern oil a thing of the past."

Within hours of each other, the automakers announced yesterday at the Chicago Auto Show plans to boost the number of E85 outlets. Only 500 of 180,000 U.S. stations sell E85 now.

GM and Ford lead Asian rivals in developing and marketing E85-compatible vehicles, called FFVs or flex-fuel vehicles. Special fuel systems and engine-computer programming are required to use E85. An FFV is otherwise identical to a gasoline vehicle, usually is priced the same, and burns any mix of gasoline and ethanol up to E85.

Ford, partnering with ethanol producer VeraSun, promises a Midwest "ethanol corridor" where E85 stations would be common. The first step will be increasing the number of E85 pumps by 30 percent in Illinois and Missouri this year, expanding to adjoining states later.

GM, with VeraSun and Shell Oil, is adding 26 Chicago-area E85 sites.

About 5 million FFVs are on the roads. Ford and GM together plan to build another 600,000 this year.

E85's drawback is reduced fuel economy. For example, GM's 2006 Chevrolet Impala sedan is rated 21 mpg in town, 31 on the highway using gasoline, but only 16 and 23 mpg on E85. Ethanol backers acknowledge that E85 must be sufficiently cheaper than gasoline to make up for the poorer mileage.

Even so, Americans dislike frequent fuel stops. A survey by AutoPacific consultants showed only 40 percent willing to accept fewer miles per gallon using E85.

GM's calling attention to its FFVs by using bright yellow fuel caps. Ford is using the children's character Kermit the Frog to promote E85.