Prices for premium gas are now about 30.2 cents over the price of regular, according to Trilby Lundberg of the Lundberg Survey. That is up from 24.1 cents in 2010 and 18.2 cents in 2000. Any increases could affect about a third of this year's car models, because premium fuel is required or recommended for them, according to Edmunds.com.
Experts disagree on the reasons for a widening gap between the costs of regular and premium gas. Reasons for the ethanol surplus are even more broadly in dispute, between producers and the oil companies. Gas companies are required under federal law to blend a certain number of gallons of ethanol into the fuel. But refiners argue that some cannot reach that requirement because they are nearing or at the so-called blend wall, the maximum percentage of ethanol in gasoline that most gas stations can handle, 10 percent. They also note that is the maximum level recommended by auto manufacturers for most cars.
Refiners blame Congress, arguing that the ethanol quota was set at a time when gasoline demand was expected to rise steadily. Instead, demand has declined, and refiners, obligated to blend more ethanol than they can actually use, have resorted to buying a lot of ethanol credits, known as renewable identification numbers (or RINs), to meet the mandated levels.