The U.S. Environmental Protection Agency delays a decision over whether to increase the amount of ethanol blended into gasoline but says its early tests show newer vehicles can tolerate a richer mix.

In a letter to Growth Energy, a lobbyist for the ethanol industry that recently requested the EPA richen the ethanol mix to 15% from the current 10%, the agency says so far its research indicates “the robust fuel, engine and emissions control systems on newer vehicles will likely be able to accommodate higher ethanol blends, such as E15.”

The EPA specifically points to ’01 and newer model-year cars and trucks.

“However, we continue to evaluate the question of component durability when E15 is used over many thousands of miles,” EPA Assistant Administrator Gina McCarthy writes, noting a study being conducted by the U.S. Department of Energy soon could reveal critical additional findings on the topic.

The DOE is testing 19 vehicles to study long-term emissions impacts on newer cars and trucks. The research should fully conclude next August, although much of the data could be available as early as June.

“Should the test results remain supportive and provide the necessary basis, we would be in a position to approve E15 for 2001 and newer vehicles in the midyear timeframe,” McCarthy says.

Given its early findings, the EPA also reveals it has begun taking steps to ensure fuel pumps are properly labeled so owners of older vehicles, or people filling up for items such as boats and lawn mowers, get the correct gasoline.

Experts have suggested alternatives such as a dial on pumps consumers can rotate to get the correct blend.

Two years ago, Congress passed an energy bill calling for the U.S. to increase the amount of renewable fuels added to gasoline to 36 billion gallons (136.2 billion L)by 2022 from a 2007 level of 4.7 million gallons (17.8 million L).

The goal is to increase the nation’s energy independence and spur development of the U.S. biofuels industry, but the bogey faces a so-called “blend wall,” where older vehicles and other equipment powered by an internal-combustion engine cannot handle the corrosive nature of a richer ethanol mix.

Currently, there are about 7 million flex-fuel vehicles on the road today that can handle an ethanol mix of 85%, and auto makers such as General Motors Co. have pledged to build more, but the availability of those pumps remains scarce.

The EPA was expected to deliver a decision today whether to grant the waiver request from Growth Energy that would raise the renewable limit to 15%.

The Alliance of Automobile Manufacturers, which represents 11 auto makers in Washington including GM, Ford Motor Co. and Toyota Motor Corp., backed the EPA’s decision to postpone granting the waiver.

AAM President Dave McCurdy says the EPA’s move will give the EPA and auto makers more time to ensure the higher blends do not negatively affect vehicle emissions, performance and durability.

“Widespread failures resulting from higher blends of ethanol would be costly to auto makers, a setback for the biofuels industry and most of all a disaster for the driving public,” he says in a statement.