Mr. Sommer’s plant, like many, is running below capacity. And as the price of corn, the main ingredient in ethanol, is pushed higher by drought, some ethanol makers are wondering if they will have to shut down. Mr. Sommer’s plant was processing 45,000 bushels of corn a day but is now down to 36,000.

The fuel makers say they are in their own bind.

“It’s the quintessential immovable object and the irresistible force,” said Charles T. Drevna, the president of the American Fuel and Petrochemical Manufacturers, a trade association. Fuel makers are supposed to use more ethanol in their blends, but carmakers say that if E15 damages engines, the repairs will not be covered by warranties. “What do you want us to do?” he said. “We can’t comply.”

Not so, say the ethanol manufacturers, which petitioned the E.P.A. to approve E15 for most cars. “The economics are so compelling right now, ethanol being about 90 cents cheaper than gasoline,” said Bob Dinneen, president and chief executive of the Renewable Fuels Association, a trade group.

He promised “meaningful savings at the pump” and predicted that when retailers like Mr. Zaremba’s station get going, competitive pressures will pull others along.

Some car experts say that the savings are illusory, because a gallon of ethanol has only about two-thirds as much energy as a gallon of gasoline, so it will take a car fewer miles on a gallon.

The ethanol industry had previously tried to expand ethanol demand by promoting E85, a fuel that is 85 percent ethanol. Although about 10 million newer-model cars on the road are capable of using E85, it has yet to catch on with gas stations or consumers.