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Volt could break 100 mpg ceiling if EPA approves

Rafay Ansar

The Chevrolet Volt could be on its way to being the first mass-produced vehicle rated at 100 mpg or more.

To ensure that happens, General Motors is asking the EPA to declare the Volt an electric vehicle for regulatory purposes. GM spokesman Rob Peterson said the California Air Resources Board has given the Volt preliminary certification as an electric.

A government rating of more than 100 mpg would give GM invaluable marketing ammunition and would be a boost for company compliance with fuel economy standards. Peterson confirmed the request today.

Loops vs. formulas

Normally, a vehicle is run on an EPA test loop, consisting of both city and highway driving, to measure tailpipe pollutants and provide data for calculating fuel economy. But for electrics, which have no emissions, the government uses a Department of Energy mathematical formula to translate energy use into some equivalent of miles per gallon of gasoline.

Using that formula, the limited-production all-electric Tesla Roadster, for example, gets rated at 244 mpg for the government's corporate average fuel economy program. Tesla officials say they look forward to being able to sell the fuel economy credits they will accumulate, even with limited sales.

The Volt is a plug-in electric hybrid, which GM calls a "range-extended" electric. Due on the market in late 2010, the Volt will be designed to go 40 miles on all-electric power. Then a small internal combustion engine would kick in to extend the range.

It appears unlikely that the government test loop could be used to accurately measure Volt emissions and fuel economy.

Removing all doubts

Simply declaring it an electric would remove any doubt.

But one government official, who insisted on anonymity, said declaring the Volt an electric would not paint a true picture. If a motorist forgets to plug in one night, then the car would run the next day using the 1.4-liter gasoline engine to generate all the electric power for the drive motor.

Peterson said if the Volt is certified as an electric vehicle, engineers could then optimize the powertrain's calibration for testing against that classification.

The Society of Automotive Engineers would not classify the Volt as an electric vehicle. SAE defines a hybrid as having two energy sources, such as gasoline and electricity. The Volt has both.

GM has not said how many miles per gallon the Volt would deliver when it is running on its gasoline engine. But the size of the Volt's fuel tank and the range GM says the vehicle can travel points to a gasoline-only fuel economy of between 35 and 50 mpg after the car's first 40 miles on pure electric power.
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