By Justin Hyde

Chevy Volt Fuel Economy: 60 MPG, Asterisks Included

The Chevy Volt's official mileage ratings: 93 mpg combined city/highway on electric, 35 miles on battery, 37 mpg on gas-only power, 379 miles of total range. Total combined EPA estimate: 60 mpg, or about 20% better than a Toyota Prius.

The final label from the U.S. Environmental Protection Agency provides a bounty of data for Volt fans and critics alike. GM says the 93 mpg electric number will get it's spotlight, maintaining that most owners will plug in every night and rarely drive beyond the car's electric-only range. That number doesn't match the 99 mpg-equivalent granted the all-electric Nissan Leaf, but it's close enough for GM's purposes.

Yet just calling the Volt a 93-mpg car is outright misleading, unless those claims give the same space to the 37 mpg rating of its gas-powered modes. Overcoming "range anxiety" is the Volt's chief technical feat, and GM itself contends customers will have to have a "holistic" view of the car's performance.

And the final EPA label shows no sign of the 230-mpg fuel economy figure that GM played up so vigorously last year. Volt executives said that number - which was roughly the highway cycle performance of the car driving on its batteries alone - was not "overly descriptive of its combined performance."

While the true 60 mpg-e figure ranks the Volt best among compact cars, it's not far removed from the 50 mpg of the Prius hybrid. Even assuming a Volt driver goes without gas for a year, by the EPA's own figures the Volt saves $263 over the Prius annually, a small gap given the Volt costs roughly $10,000 more.

GM has a reason to celebrate today: The last hurdle in its four-year march to build a plug-in hybrid has finally been cleared. In doing so, Volt customers can now figure out for themselves just how well it works for them - or whether there are better ways to save.