Drivers Don't Drive Less—They Use Cheaper Fuel

Passing up premium gas offers an easy way to save 20 cents per gallon.

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High prices do not appear to have moved U.S. drivers to use less gasoline, but motorists have turned to cheaper grades of fuel. This is one of the findings of a new Congressional Budget Office study on how gasoline prices affect driving behavior. The study's main conclusion appears to be that there have been slight changes, but some of the findings—people are driving slower to save gas?—are so hard to believe that I'd like to return to them another time.

Yet there are actually solid statistics—again from the U.S. Energy Information Administration—to show that between 2000 and 2007, consumption of premium gasoline fell 25 percent and that of medium grade dropped 35 percent, while regular gas sales—always much larger—increased 6.7 percent. Total gasoline sales, by the way, climbed 7 percent in those seven years. Back in 2000, regular grade made up 77 percent of all gasoline sales. That share was up to about 85 percent in 2007, while premium sales were just 9.5 percent of the market and midgrade was the laggard at 5.7 percent.

By choosing regular grade over premium, drivers can save about 20 cents per gallon. But are they ruining their engines if the manufacturer recommends a higher-octane fuel to prevent pinging or knocking and improve performance? Both the California Energy Commission and the auto information site Edmunds say there is no problem.

By recommending a higher-octane fuel, your auto manufacturer can boast that your car has more horsepower. But the power loss of downgrading will be barely noticeable to most drivers, and improved auto engineering means that you probably won't even hear any knocking or pounding noise in your engine because of less-than-perfect combustion of the fuel. (According to the Society of Automotive Engineers, regular gas has an octane rating of at least 87, midgrade at least 89, and premium 91 or more.)

The SAE, however, does urge that you follow the auto manufacturers' recommendation, and I found this 2001 article in Car and Driver citing issues that could arise for higher-performance cars. It also goes on to call fuel downgraders cheapskates.

Of course, the cheapskates buying regular gasoline today are paying a whole lot more today than the performance mavens who bought premium back then.