WASHINGTON -- Nearly two thirds of drivers could have more corn-based ethanol in their fuel tanks under an Environmental Protection Agency decision Friday.

The agency said that 15 percent ethanol blended with gasoline is safe for cars and light-duty trucks manufactured between 2001 and 2006, expanding an October decision that the higher blend is safe for cars built since 2007.The maximum gasoline blend has been 10 percent ethanol.

The fuel is popular in farm country because most ethanol comes from corn and other grains. It faces strong opposition, however, from the auto industry, environmentalists, cattle ranchers, food companies and a broad coalition of other groups. Those groups say ethanol use makes animal feed more expensive, raises prices at the grocery store and tears up the land. There have already been several lawsuits filed against the EPA since the agency decided to allow the higher blends for newer cars in October.

Critics said the change could be frustrating for drivers of older cars who will have to figure out which service station pump to use. And they argue that many retailers will opt not to sell the higher blend because of the expense of adding new pumps and signs.

"It seems like corn growers and the ethanol industry are the only real winners here," said Craig Cox of the Environmental Working Group, an advocacy group that opposes use of the fuel.

The Obama administration has remained supportive of the renewable fuel, and the EPA has said a congressional mandate for increased ethanol use can't be achieved without allowing higher percentage blends. Congress has required refiners to blend 36 billion gallons of biofuels, mostly ethanol, into auto fuel by 2022.

Members of the ethanol industry say that use of the fuel can help reduce the country's dependence on foreign oil while boosting a domestic industry and creating jobs. The industry group Growth Energy petitioned the EPA to raise the blend in March 2009. Tom Buis, president of the group, said Friday there are still steps to go to get more ethanol on the market but he is optimistic.

"Ultimately we will get this marketplace open because it's a win for America, a win for consumers and a win for our economy," he said.

The EPA has said there won't be a decision any time soon on boosting the ethanol concentration for cars and light trucks manufactured before 2001 - or for motorcycles, heavy-duty vehicles or non-road engines - because there is not sufficient testing to support such an approval.

The EPA has delayed decisions on using 15 percent ethanol several times as the agency and the Energy Department have tested the ethanol-blended gasoline to make sure it is safe. The agency has approved the blend only for newer cars and trucks because they have more durable emissions systems.

Ethanol burns hotter than gasoline, causing catalytic converters, which help clean engine emissions, to break down faster.