Prices Fuel a Rebellion

"What did she get?" Wangkang asked his cashier, who checked her receipt.

"Regular," he replied.

The first drivers to defect from premium, station managers say, are those whose cars don't specify a need for premium gasoline but who were using it anyway, thinking it might help -- even though most experts say it won't. But even owners of cars that purport to require high-test -- complete with a warning on the gas cap, "Premium Fuel Only" -- also are trading down.

David Shapiro said he and his wife switched to regular independently of each other about two weeks ago. It was a spur-of-the-moment decision for the tax lawyer with the D.C. office of PricewaterhouseCoopers.

"I never really knew if it made a difference, and I figured it was time to try and see if my car really works fine," he said of his Volvo, which recommends premium fuel. "It's like two bucks a tank difference, so it's like a free gallon. And it hasn't made a bit of difference in how the car drives."

Although the numbers are slightly different in some states, premium fuel typically has an octane rating of 91 while regular fuel's rating is 87. Octane controls the fuel-air mixture in an engine to keep it from igniting before it's supposed to, which can cause reduced power and harmful knocking. But in all modern cars, computers adjust the timing of the engine's compression so that "pre-ignition" never happens, said Cole Quinnell, a spokesman for Chrysler Group Engineering.

"It does not hurt the engine -- sensors automatically readjust the engine basically for that reason, to save itself," he said.

Chrysler recommends 91-octane fuel for its high-performance and turbocharged automobiles, such as the SRT models, "but all our products will run on 87 or 89," Quinnell said. Any loss in performance would come when an engine is pushing to its maximum power and speed, he said, so "if an average driver got into one of our SRT vehicles, they wouldn't notice any change."

Karl Brauer, editor in chief of Edmunds.com, an automotive information and research firm, said carmakers perpetuate the premium fuel requirement because engines designed for that gas can achieve greater performance when powered by the high-grade fuel.

"Manufacturers want to be able to quote high horsepower numbers," Brauer said. "If it's not run on premium, it probably won't ever hurt the car. It probably won't ever be noticed by most drivers. But they can still have their claimed horsepower for their brochures."

Oil refiners make the most money from selling higher-grade gasoline because the higher cost to produce it is more than made up by the added charge to customers, said Fadel Gheit, an oil analyst at Oppenheimer & Co. in New York. Gas stations also benefit from higher margins on premium fuel.

"It's to everybody's advantage to push the high-grade," Gheit said.

For their part, the oil companies say they're just providing the fuel that carmakers demand. "We're guided by what the car manufacturers say and what the octane requirement would be, so our responsibility is to fill the need and provide what the consumer would require for their cars to work most efficiently," said Gerald T. Davis, a spokesman for Sunoco. Asked if premium gasoline is more profitable for the oil company, Davis would say only, "Our gasoline is priced competitively and fairly."

Staff writer Justin Blum contributed to this report.