CONCORD, N.C. (AP) — NASCAR will move from unleaded fuel to an ethanol blend in all three of its national series beginning next season.

The switch to Sunoco Green E15 was announced Saturday by NASCAR chairman Brian France, who touted the switch as yet another step by the auto racing series toward environment friendly practices.

"This is the most visible thing that we can do to let our partners and our fans know that NASCAR is taking a slow, steady march as an industry," France said at Charlotte Motor Speedway.

The E15 blend is a mixture of 15 percent ethanol and 85 percent gasoline. It is a clean-burning, high-octane motor fuel, and the ethanol portion is produced from renewable resources that Sunoco will get from the Midwest.

"Domestic ethanol, for sure," France said.

The blend will replace Sunoco 260 GTX, a 98-octane fuel that is currently used at all three of NASCAR's national divisions. NASCAR made the move, with Sunoco, from leaded to unleaded gasoline at the start of the 2007 season.

Now comes a long-overdue change to an ethanol blend, which becomes NASCAR's most significant green initiative. Others include a program that plants 10 trees for every green flag waved in a Sprint Cup race; a recycling program NASCAR touts as the largest in professional sports; Pocono Raceway, the world's largest solar-powered sports facility; and two new LEED certified "green buildings" that house NASCAR's offices in Charlotte and Daytona Beach, Fla.

But the ethanol fuel is their most advanced move yet.

"When we said we had to accelerate our green efforts, this was a centerpiece," France said. "It's certainly the most visible thing we can do. It's also one of the more difficult things that we do."

The E15 fuel will be blended at Sunoco's facility in Marcus Hook, Pa. The new fuel will be pumped directly from tankers at the track, rather than from onsite underground storage tanks.

Bob Owens, senior vice president of Sunoco, said development was a tricky process of overcoming reactions that occur when the ethanol and hydrocarbon are mixed and come into moisture from humidity or rain. A second issue was developing a strict chain of custody from mixture to the gas cans at the race track. The cans must be altered to eliminate any possibility of moisture contaminating the fuel.

"We didn't just take Sunoco race fuel and dump 15 percent ethanol on top of it," Owens said. "We did a significant amount of testing, and research of our own prior to getting it to the teams for their testing to ensure that we had the proper blend.

"Worst case: seamless transition. The best case, we were not surprised to hear of a little bit of horsepower gain."

NASCAR vice president of competition Robin Pemberton said some teams already have tested the new fuel. It's too soon to determine how much of a horsepower gain teams noticed, but the fuel mileage effects were minimal, Pemberton said.

"We've had several hundred-mile runs at racetracks, and everything looks to be great as far as performance goes," Pemberton said. "Probably better than we had first anticipated."