An ethanol-blended gasoline approved for use in U.S. vehicles manufactured since model year 2001 may confuse consumers and lead to damaged car engines, the American Automobile Association said.

A survey by the biggest U.S. driving organization showed that the standard for the E15 gasoline blend, issued by the Environmental Protection Agency in June, is unknown to 95 percent of consumers contacted by telephone. Less than a fifth of cars on the road have been approved by manufacturers to use the fuel, and engine damage may not be covered under warranties, AAA said.

"There is a strong possibility that many motorists may improperly fill up using this gasoline and damage their vehicle," AAA President Robert Darbelnet said Friday in a statement. "Bringing E15 to the market without adequate safeguards does not responsibly meet the needs of consumers."

Ethanol, fermented from grain such as corn, must be blended into gasoline under the Renewable Fuels Standard as a way to cut the amounts of crude oil used to make motor fuel. It's typically sold at filling stations in a formula known as E10, with 10 percent ethanol mixed with 90 percent gasoline.

Nine U.S. gas stations sell E15 fuel, according to Growth Energy, a Washington-based group that represents ethanol producers. E15 sales began in July. Seven of the outlets are in Kansas; Iowa and Nebraska have one each.

The E15 blend, which uses 15 percent ethanol, may lead to accelerated engine wear and failure, fuel-system damage and false "check engine" lights when used for sustained periods in vehicles not cleared for use, AAA said in its statement, which referenced previous research.

Wisconsin Republican Rep. James Sensenbrenner said the study supports his call to halt the sale of the ethanol blend. He has offered legislation that would require the EPA to work with the National Academies of Sciences on a study of E15.

"Concerns about E15 are not diminishing; they are increasing," he said in a statement.

Stations aren't required to sell the fuel. The EPA and the Federal Trade Commission require E15 sellers to post a "prominent orange and black label" to let consumers know a pump contains E15, said EPA spokeswoman Julia Valentine.