Some Treasure Valley drivers are going out of their way to fill their tanks with pure fossil-fuel gasoline instead of the gasoline-ethanol mixture now sold at most pumps in Idaho.

Gasoline blended with 10 percent ethanol has become predominant in the past year in response to federal mandates intended to promote cleaner energy sources. Ethanol burns more cleanly than fossil fuels, which is good for air quality.

But detractors say ethanol provides less energy per gallon than gasoline, so it reduces mileage and is hard on some engines.

Dave Conley's Phillips 66 stations in Boise and Meridian are two of the few in the area that still sell only unblended gasoline.

Conley and some of his customers say they get better mileage and their cars run better on the pure gasoline than they do on the ethanol blend.

"We were offered it (ethanol blended gasoline) this spring when everyone changed over," Conley said. "You could buy it for less, too, between 7 and 10 cents less per gallon, which is a lot."

Conley said his customers begged him not to make the change, and he intends to keep giving them what they want.

"We have too many people coming in and telling us how much more gas mileage they get and that their cars are running better - they don't ping as much," he said.

Some customers are concerned about the effect of alcohol on their two-stroke engines, too.

"We have people with snow machines and lawn mowers and ATVs, and it's a big deal for them," he said.

BILL SHAFFER'S BALKY LAWN MOWER

Bill Shaffer goes a couple miles out of the way to fill his 2003 Saturn and his 1980 Dodge motor home with unblended gas at Conley's Boise store at 8160 Overland Road. He said he made the switch after having troubles starting his lawn mower this summer.

"I told my mechanic and he said, 'Man, quit using the ethanol immediately,'" Shaffer said. "I drained the tank and got new gas, and it has run perfectly ever since."

Jim Owlsley, another customer, swears he'll never put ethanol into his 1990 Toyota truck again. He says it runs more smoothly and gets better mileage than it did when he bought gas at the truck stop next to Conley's station near his home.

"I'd drive across town to get it if I had to," he said.

Modern cars are made to accommodate the alcohol, and it shouldn't cause mechanical trouble, mechanics say.

"We haven't seen problems associated with it," said Earl Nau, service consultant at Oakley Moody Service, 1375 Grove St., Boise. "It used to be that alcohol products would eat through fuel lines and such, but that isn't really a problem any more."

ETHANOL DRAWS MOISTURE

Older, carbureted vehicles and two-stroke engines like those in lawn mowers and some motorcycles require more care if ethanol is burned in them. Owners of older boats with fiberglass fuel tanks should avoid ethanol since alcohol damages fiberglass.

"Being an alcohol product, it (ethanol) draws moisture out of the air," said Curt Sullivan, sales manager at Valley Tools, 4141 Chinden in Garden City, which repairs small engines. "We see a lot of rusted carbs and issues associated with contaminated fuel."

Sullivan said his shop sees more engine wear because of the fuel, too. Ethanol doesn't burn as hot as gas, so engines have to work harder to compensate, he said.

He said that the blended gas deteriorates faster than unblended gas He recommends keeping no more than a 30-day supply on hand and using fuel stabilizer in every can of gas.

"If you're using springtime fuel in the fall, you're setting yourself up for a visit to the shop," he said.

AAA Idaho lists 15 area gas stations on its Web site that still sell unblended fuel. Spokesman Dave Carlson said the list may not be complete, but it will probably shrink, not grow.

ETHANOL-FREE GAS TO DISAPPEAR SOON?

"We don't think there will be ethanol-free gas in the marketplace in the next year or so," Carlson said. "Ninety-five percent of the local marketplace has gone to ethanol because there are huge financial pressures to do it."

In 2007 Congress mandated that 9 billion gallons of ethanol be blended into the U.S. fuel supply this year. The federal government provides tax credits of 51 cents per gallon on pure ethanol, 5.1 cents per gallon on 10 percent blends known as E10, and 42 cents per gallon on 85 percent ethanol blends known as E85, according to the American Coalition for Ethanol, an industry lobbying group. Ethanol is also expempt from Idaho's 25 cent a gallon gasoline tax.

As a result, fuel distributors have increased their ethanol blending. Idaho has two ethanol plants: one in Caldwell that uses potatoes and a new one in Burley that uses corn. The Treasure Valley's gasoline is pumped through a pipeline from Utah, and ethanol is added after the gas arrives here.

Pumps dispensing the blends should be labeled, but some are not.

Two Treasure Valley stations sell E85, which is suitable only for hybrid cars set up to run on it: the Stinker Stations at 2323 W. Main St. in Boise and at 3319 Garrity Blvd. in Nampa.

AAA's Carlson thinks retailers should be required to clearly label the pumps so drivers know exactly what they are buying, but he admits "that may be a moot point if everyone is selling ethanol."

STREET RODDER DOUBTS ETHANOL'S BENEFITS

Car enthusiasts are not convinced that unblended gasoline will go the way of leaded fuel.

"The debate may be swinging the other way," said Curtis Stoddard, president of United Street Rods of Idaho, which has 600 members. Stoddard said he had to drain the entire fuel system of his 1966 GTO after one tank of E10 fuel. "It was full of water," he said.

Stoddard says questions about the high price of ethanol's raw materials - mostly corn - and increasing questions about the true environmental benefits of the fuel lead him to believe ethanol growth is not guaranteed.

In the short term, he said, his members don't seem too concerned about the issue. They can still find nonethanol gas fairly easily. Stoddard fills his GTO and his motorcycle at 7-Eleven stores that pump unblended gas, but uses E10 in his daily vehicle.

Brad Talbutt: 672-6737