Fuel Economy of Gasoline Vehicles

Summary

  • It is difficult for a driver to measure fuel economy changes of less than 5 percent, which is one mile per gallon (mpg) for a vehicle with a fuel economy of 20 mpg. In the aggregate, however, even much smaller improvements in fuel economy are significant.
  • Selecting the most fuel-efficient vehicle that meets the driver's needs is more beneficial than any other efforts to save fuel.
  • Maintaining a vehicle and driving conservatively improve fuel economy.
  • The fuel economy of gasolines in the marketplace varies about plus or minus 3 percent — excluding the impact of oxygenates.
  • The average fuel economy of reformulated gasoline (RFG) is 2 percent to 3 percent lower than that of conventional gasoline.
  • In some vehicles the fuel economy of oxygenated RFG or oxygenated gasoline may diverge widely from the average — decreasing much more than 3 percent, or actually increasing.

Fuel Economy Shorthand

Rigorously, fuel economy is a property of a fuel/vehicle combination; separately, neither a vehicle nor a gasoline have a fuel economy. However, statements about the fuel economy of vehicles rarely refer to the gasoline used to obtain the value. This bulletin, using a similar shorthand, discusses the fuel economy of gasoline and how it varies. It should be understood that the values are those that would be observed if the variety of gasolines were tested in an average vehicle.

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