General Motors’ upcoming Volt plug-in gasoline-electric hybrid has already grabbed plenty of buzz over the past couple of years. But Volt mania reached a fever pitch this summer when General Motors announced that it would achieve 230 miles per gallon.
Before you go put your money down, beware—neither of those two numbers are official U.S. Environmental Protection Agency (EPA) fuel economy estimates. TheEPA hasn’t yet formalized any method of testing or rating plug-in hybrid vehicles or a new generation of electric vehicles, and you won’t find either of those numbers in the EPA’s annual Fuel Economy Guide or on window stickers because they’re still prototypes.
Turns out both of these triple-digit numbers rely on optimistic methodologies that are favorable for the respective vehicles but not or easily applied to other types of vehicles or compared to present-day fuel economy figures.
The recent claims remind John DeCicco, a transportation and energy issues expert, of the time just after the 1973 oil crisis and before the first official EPA fuel economy ratings were available, in 1975. Some manufacturers around at that time advertised their vehicles with “outlandish mileage claims,” recalledDeCicco, also a senior lecturer on energy and climate policy at the University of Michigan. “We’ve again got a situation where manufacturers will spin the number to look good,” he said.
Looking at the 230-mpg figure, there’s no way of saying simply that the Volt would use less than a quarter of the fuel of a 50-mpg Toyota Prius to go the same distance.
It is however fair to say that in typical driving a 50-mpg Prius will go twice as far on a gallon of gas as a 2010 Toyota Corolla XRS, rated at 25 mpg. Such comparisons are fair game for any light vehicle that’s officially on sale in the U.S. Every one carries EPA fuel economy ratings, which are designed to give prospective owners an idea of relative fuel cost in real-world driving as well as a way of comparing various models on equal ground.
The ratings are listed in the EPA’s annual Fuel Economy Guide, at fueleconomy.gov, or on the window sticker of any new vehicle; they’re also used in figuring an automaker’s corporate average fuel economy (CAFE) and in assessing a gas-guzzler tax on some vehicles. They’ve become an important way in which shoppers can easily compare one vehicle to another, and it assures a level playing field because of rigorous testing.