The corn ethanol industry, joined by a group of Midwestern governors, welcomed the fall driving season Wednesday by asking the Environmental Protection Agency to lift restrictions on the amount of ethanol in the nation's gasoline supply.

The Renewable Fuels Association, the leading trade group for the ethanol industry, said Wednesday that the restrictions on the use of 15 percent ethanol fuels are the fault of the EPA, which approved waivers for the fuel's use five years ago, but refused to grant it special allowances for vapor pressure that would allow it to be sold year-round.

The EPA essentially bans the use of the fuel from June 1-Sept. 15 because it says the higher volatility of the 15 percent blend could worsen air quality in the summer.

The oil industry argues against the use of 15 percent ethanol fuels, saying the majority of cars in the country cannot use it, and higher amounts of ethanol in the fuel supply can damage vehicle engines. The ethanol industry believes differently and argues air quality would improve with more of the fuel being sold.

The EPA's "arcane" seasonal restrictions for E15 fuel will be lifted for the year Thursday, giving "consumer choice at the pump ... a shot in the arm," the trade group said.

A group of seven Midwest governors sent a letter to EPA Administrator Gina McCarthy on Tuesday asking her to lift the restrictions for the entire year.

"We write to ask you to remove a significant regulatory obstacle that is preventing large-scale availability and use of E15 and mid-level ethanol blends," the letter said, signed by five Republican and two Democratic governors.

The governors included Terry Branstad of Iowa, Sam Brownback of Kansas, Mark Dayton of Minnesota, Jeremiah (Jay) Nixon of Missouri, Pete Ricketts of Nebraska, Jack Dalrymple of North Dakota and Dennis Daugaard of South Dakota. Dayton and Nixon are the two Democrats who signed the letter.

Most of the nation's gasoline is a blend of 90 percent gasoline and 10 percent ethanol, called E10. The EPA requires that refiners blend an increasing amount of corn ethanol and other biofuels into the nation's gasoline and diesel supplies under a program called the Renewable Fuel Standard.

As the EPA program required higher amounts of renewable fuel to be blended since 2010, the ethanol industry asked the agency to approve a waiver to allow the use of 15 percent blends in cars.

The EPA approved the waiver in 2011, allowing the ethanol fuel to be used in 2001 and higher model-year vehicles, fearing older cars would experience damage from using the fuel.

The governors said 300 fuel stations of the nation's 150,000 have the special pumps required to sell E-15. But they say the market would grow significantly with the vapor pressure restriction removed. The pumps they are referring to, called "blender pumps," allow drivers to choose the level of ethanol in gasoline.

"Station owners tell us that the greatest obstacle to offering E15 is the inequitable [vapor pressure] regulation of E10 and E15," in which E10 gets the allowance but E15 does not.

The governors told McCarthy that the "unbalanced" treatment between the fuels "makes it extraordinarily difficult for retailers in a conventional fuel area to offer E15 year-round as a registered fuel."

Since ethanol fuels have a higher vapor pressure rating than gasoline, they cannot qualify for use in cars without the EPA granting a waiver. The agency granted it for 10 percent blends as far back as 1989, but said it wasn't possible for 15 percent blends due to air quality concerns.

The EPA also imposes summer gasoline volatility restrictions, which makes it next to impossible to allow E15 to qualify. Those who wish to sell the higher ethanol fuel have to wait until Sept. 15, when the fuel restrictions are lifted.

"EPA's continued inaction on the summertime volatility restrictions is stifling the growth of higher ethanol blends and incorrectly using that as justification to propose lower 2017 Renewable Fuel Standard targets. We reiterate the need for EPA to address this issue," said Renewable Fuels Association President Bob Dinneen.

The group said two Midwest fuel distribution companies are preparing to come onboard in support of the 15 percent ethanol blend beginning Friday. That will be followed by about 1,500 new stations offering E15 in the coming months.