230 MPG For Chevy Volt? Not Anymore

April 22, 2010

2 Min Read
230 MPG For Chevy Volt? Not Anymore

Will Nissan be able to claim that its all-electric Leaf will get 367 mpg? Will the Chevy Volt be rated at 230 mpg? Apparently not, according to The Wall Street Journal.

            The Journal reported this week that the EPA’s draft methodology – the same one that caused Nissan and General Motors to make their outlandish claims – will be changed. The newspaper says that the government “is rethinking the way to calculate fuel efficiency ratings for electric vehicles.”

            For those who missed the flap over those numbers last summer, here’s a capsule summary: Last August, former-GM CEO Fritz Henderson grandly announced that GM expected the Chevy Volt to achieve city fuel economy of 230 mpg. Within days, Henderson’s shocking pronouncement was one-upped by Nissan, which said that the Leaf would get an even-more dazzling 367 mpg.

            As soon as the word came out, headline writers at major newspapers began hyperventilating. Amidst all the headlines, however, those who understood the technology were puzzled. How, they asked, could the Nissan Leaf get 367 mpg when it doesn’t burn a drop of gasoline?

            Good question. The answer lay within a draft methodology created by the Environmental Protection Agency. The numbers, they said, were miles per gallon equivalents (called MPGe). The EPA wouldn’t comment on how MPGe worked, but Nissan did tell us that they calculated their 367-mpg figure as follows: The Leaf, they said, consumes 0.223 kWh/mile. By dividing that number into 82.048 kWh/gallon (a gasoline equivalency number they got from the EPA), they reached the now famous (or infamous) figure of 367 mpg.

            But when those numbers were publicized, many observers rightly argued that they had little or no meaning. “We love to see progress,” noted John Shore, senior advisor to the Automotive X Prize Foundation. “But right now, beyond saying these cars are getting good fuel efficiency, we don’t know how meaningful it all is.”

            So now EPA staff is said to be finalizing a new formula that will deliver “more down-to-earth ratings.” Nissan and GM, meanwhile, are no longer commenting on their mileage numbers. Both companies are reportedly waiting on a finalized formula before making any statements.

            Whatever methodology is employed, most engineers are in agreement on one key point: It needs to be transparent.

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