Susan Blakey is a gasoline connoisseur. She drives by stations that sell fuel mixed with ethanol for purer stuff that gives her better mileage than blends.

“I wouldn't use it unless absolutely nothing else was available,” Blakey said.

Ethanol, added to gasoline for years, is being avoided by some drivers as pump prices soar and the plant-based additive becomes more prevalent. A few of the consumers are merely suspicious, like the blogger who wrote “I don't want CORN in my car.” Others worry about lower fuel efficiency. Stuck with paying $4 or more per gallon, they want to extract every penny of value from their fill-ups.

“It's mainly for the pocketbook,” said Beth Corcoran, who said she and her husband drive by cheaper gas at her local Wal-Mart in a suburb of Oklahoma City in favor of pricier, no-ethanol gas. She says the better miles per gallon saves her family money in the long run.

Most gasoline sold in the United States is now mixed with up to 10 percent ethanol, according to industry estimates. Often called E10, the use of the blended fuel has grown with a federal mandate designed to boost the levels of renewable fuels at the pump. It's the only sort of gasoline sold in many areas. The mix is designed to be compatible with most vehicles on the road, as opposed to the 85 percent ethanol blend called E85, used in “flexible fuel” vehicles.

Advocates promote ethanol as a homegrown fuel that reduces the country's dependence on foreign oil, though it has lost some of its luster in the past year amid a surge in corn prices. Still, since ethanol is less expensive than gasoline, stations that sell ethanol blends can shave a bit off the per-gallon price.

But even at cheaper prices, some drivers say it's still not worth it because of mileage losses.

A gallon of ethanol has less energy than a gallon of gasoline. The federal Department of Energy says it takes 1.03 gallons of E10 for a vehicle to cover the same distance that it would with a gallon of gasoline.

Actual road results may differ.

Corcoran said her husband's Honda Accord got a bit more than 30 mpg on “pure” gasoline versus 25 mpg on E10. Blakey, who lives in O'Fallon, Ill., soured on E10 after noticing a big drop in mileage in her family's 2002 LeSabre on a trip to visit her daughter in Ohio.

“It's huge, huge difference,” she said.

Ron Lamberty, a vice president of the American Coalition for Ethanol, an industry group, said many vehicles running on E10 will experience a 3 to 4 percent drop in fuel efficiency, though some vehicles actually see a slight increase because of E10's higher octane rating.

Lamberty said mileage critics are not taking a larger picture into account. Ethanol burns cleaner, creates jobs, is good for fuel-injection systems and - by reducing overall demand - reduces gasoline prices.

Lamberty contends that the mileage issue is not a large one, using an example of a car that can travel 300 miles of a tank of gas. If it experiences a 3 percent drop in fuel efficiency on E10, that equals nine fewer miles per tank.

“It's not a lot of miles,” Lamberty said. “It's not like you're all of the sudden not going to have to go the station one day.”

Regardless, choosy drivers continue to hunt out “pure” gasoline in areas where reformulated gasoline is not required. Some states, like New York, require labels at the pumps like: “Contains up to 10% Ethanol.” Some stations do more, like the Citgo retailer along Route 9 in upstate New York just south of the Adirondacks with a big sign reading “NO ETHANOL 100% GAS.” The station's prices on a recent day were one to two cents less a gallon than stations down the road selling blends.

One Web bulletin board includes a map of where to buy ethanol-free gasoline in Tampa.

Still, the search will likely get harder in the coming years.

There are at least 11 states with blending requirements, include California, where fuels must have 6 percent ethanol as an oxygenate. The federal Renewable Fuel Standard, which requires increasing use of renewable fuels every year, is expected to spur more ethanol production in the coming years. Florida this summer adopted a law that will require blends by the end of 2010.

“It is becoming increasingly widespread,” said Brandon Wright of the Petroleum Marketers Association of America.

AP-ES-07-27-08 1421EDT