It's one of America's best kept secrets: The U.S. automobile industry has been manufacturing ethanol-compatible motor vehicles for at least three years.

Some Americans — as many as 1 million, industry spokesmen say — may in fact already be driving “flexible-fuel” cars and trucks but are unaware of it. Ethanol proponents, including U.S. corn groups, say the oil industry would prefer they never know.

As American motorists watch gasoline prices soar, and as they grow especially nervous about summertime price “spikes,” many drivers would welcome news that they may be able to fill up with a cheaper mix of gasoline and ethanol.

The American Automobile Association says the price of regular grade unleaded gasoline has jumped in some Midwestern states to as high as $1.96 a gallon on average in Illinois, second only to California's $2.01 a gallon. Some industry observers fear prices could rise to $3 a gallon this summer.

Ironically, the price of gasoline is often highest in the Midwest — the nation's Corn Belt, where most ethanol is processed. That is also where a motorist who could use it if he had it is most likely to find it.

That's the rub — or part of it. The Reuters News agency reported in May that there are fewer than 200 fueling stations that retail “E85,” a federally subsidized blend of 85 percent ethanol and 15 percent gasoline. Flexible-blend motor vehicles can use both E85 and standard fuel or a mixture of the two.

The trade publication Oxy-Fuel News says the average price of E85 ethanol-gas mix is about $1.65 in the Midwest states — 31 cents per gallon cheaper on average in Illinois than regular gasoline.

Auto industry sources say General Motors Corp., Ford Motor Co., and DaimlerChrysler have manufactured over the last three years an estimated 1.2 million cars and trucks fitted with fuel-flexible systems. Fuel-flexible systems help automakers meet stringent fuel-economy standards.

Automakers, however, have not marketed the vehicles aggressively, a General Motors spokesman says. As a result, says GM's Sharon Bedley-Parham, “the customer may order an ethanol-compatible vehicle without knowing it.”

President Bush's recent energy report acknowledged the lack of ethanol use at the nation's pumps, but added that further study must be done to promote its use.

The E85 system is fitted as standard equipment, at no extra charge, on many versions of some of the most popular-selling vehicles, including the Ford Taurus mid-size car, DaimlerChrysler's Dodge, Chrysler and Plymouth minivans, and GM's Chevrolet Tahoe and Suburban large sport utility vehicles.

Because E85 actually has a higher octane rating than regular unleaded gasoline, drivers may notice better performance and a sweeter-smelling exhaust. Otherwise, industry sources say, there is almost no perceptible difference.

In the meantime, mass ethanol use and production are slowed by the limitations of established infrasture and by the driving public's perception that ethanol blends actually raise the price of gasoline.

Corn groups have said for years that ethanol can be transported across the continent as easily as oil, and if motorists were more aware of cost savings, improved vehicle performance, and the availability of fexible-fuel vehicles, the demand for ethanol would correct the shortage of ethanol outlets.

e-mail: ben_pryor@intertec.com