WASHINGTON - Ethanol producers asked the Environmental Protection Agency on Friday to boost the amount of ethanol that can be blended with gasoline, but automakers argued the increase could damage car engines and fuel lines.

The ethanol producers want the EPA to increase the amount of ethanol that refiners can blend with gasoline from a maximum of 10 percent to 15 percent, which could boost the demand for the renewable fuel additive by as much as 6 billion gallons a year.

"Increasing the ethanol blend up to E15 is a common sense solution to our economic, energy and environmental challenges," said retired Gen. Wesley Clark, co-chairman of Growth Energy, a coalition of ethanol companies.

The group argued that a number of studies, including one by the Energy Department, has shown that a 15 percent ethanol blend "has no adverse effects on a car's performance, maintenance, or emissions controls."

The ethanol producers contend that by raising the maximum amount of ethanol allowed in a gallon of gasoline, it would increase demand for the fuel additive and create thousands of new jobs as the industry - which has been reeling in today's tough economic times - boosts production.

"If the EPA acts swiftly, a higher blend of ethanol will help us jump-start the economy while further reducing our dependence on foreign oil," Clark said.

EPA press secretary Adora Andy said in a statement that the agency will review the request and "will act based on the best available science."

But automakers and the producers of outdoor power equipment say the science has not yet shown that the higher "midlevel" blend of ethanol will safeguard engines, fuel lines, emission controls and other components.

"There has not been sufficient testing of motor vehicles and non-road power equipment … to determine whether any midlevel ethanol blend would meet current federal air quality protection requirements or be safe for consumers to use," said a coalition whose members included automakers, boat owners, motorcycle manufacturers and oil refiners.

Charles Territo, a spokesman for the Alliance for Automobile Manufacturers, said, "The best way to increase ethanol use is to expand" the infrastructure for providing 85-percent blend fuel. The E-85 fuel requires so-called "flex-fuel" vehicles of which there are about 6 million on the road.

Kris Kiser, executive director of the Outdoor Power Equipment Institute, said boat engines, chainsaws, lawn mowers, snowmobiles, motorcycles, generators and other small engine equipment "may be permanently damaged" from using the 15 percent ethanol blend.

North Dakota Agriculture Commissioner Roger Johnson said he was among agriculture officials from 10 states who wrote a letter to President Barack Obama, urging him to support the production and use of fuel blends that contain more ethanol.

"Now is the time to move forward by increasing the base fuel blend to 15 or 20 percent ethanol," Johnson said.

Ethanol producers contend that even if the blend cap were increased, plenty of 10-percent ethanol blended gasoline would be available for use on such equipment.

Producers supplied 9.2 billion gallons of ethanol last year. The government mandate requires refiners to blend about 11 billion gallons of ethanol with gasoline this year. Producers argue the 10 percent content limit may make it difficult to achieve the federal mandate because ethanol use in some parts of the country is limited by transportation constraints.