Major automakers asked the U.S. Environmental Protection Agency not to approve higher blends of ethanol in gasoline until the agency has adequate test results showing the fuel would not damage vehicles.

Ethanol is now approved to make up 10 percent of U.S. gasoline in cars and trucks. Ethanol producers want the government to allow higher ethanol blend levels up to 15 percent, or E15, as more ethanol will be required each year under federal law.

However, the Alliance of Automobile Manufacturers said increasing the blend rate to beyond 10 percent ethanol, or E10, would affect vehicle emissions, performance and durability.

We urge EPA to delay any decision on blends higher than E10 for the existing fleet until adequate testing results are available, the group said in a comment letter sent to the agency on Monday.

The trade group represents 11 car and light truck manufacturers including BMW Group, Chrysler, Ford, General Motors, Jaguar Land Rover, Mazda, Mercedes-Benz, Mitsubishi Motors, Porsche, Toyota and Volkswagen.

The group said because the EPA has never allowed automakers to use gasoline blends with more than 10 percent ethanol, companies have never had a reason to design, test or warrant vehicles for the U.S. market that use higher ethanol blends.

EPA lacks sufficient data to make a sound-science based judgment about E15 (or any gasoline-ethanol blend between E10 and E15), the group said.

Growth Energy, the association of U.S. ethanol producers which requested the higher blend, said its position is supported by science.

Multiple studies by government agencies and academic institutions, conducted on more than 100 vehicles, 85 engine types and 33 fuel dispensing units all conclude that E15 has no adverse impact on an engine's performance, maintenance or emissions, Growth Energy CEO Tom Buis said in a statement.

Opponents to the waiver have yet to show any solid evidence that is contrary to this overwhelming science, Buis added.

Congress required 9 billion gallons (34 billion liters) of ethanol and other biofuels to be blended into gasoline last year. The amount will rise annually toward 36 billion gallons a year in 2022.

The EPA has until December 1 to decide whether to allow a higher ethanol blend beyond the current E10 level.