GM argues that altering the test in the way the EPA proposes -- requiring the Volt finish the test with batteries near full charge -- is unfair and won't reflect reality. Moreover, in everyday commuting, the Volt will be an electric car for its first 40 miles, not ever even firing its engine for drivers with commutes short enough or recharging ability at work. The EPA's motivation is to come up with a meaningful mileage rating for the Volt, which will ace the current test. If the Volt gets a rating that is artificially low because the EPA can't figure out a test that correlates to reality, it could also hurt the Volt's case with consumers looking at the $40,000 price tag next to numbers barely better than what a diesel or parallel hybrid can earn.
[Source: Motor Trend]