GM Claims a 230 MPG Volt — Is it For Real?

General Motors made a media splash this morning by announcing that its Chevy Volt would get 230 miles per gallon in city driving, but the claim quickly began proving little more than a broad estimate.

The stage for GM's announcement today. (Photo: CNN)

GM based its Volt claim on draft rules from the Environmental Protection Agency (EPA). The agency promptly noted that the 230-mpg estimate -- which does not include less fuel-efficient highway driving -- could not be confirmed in a statement to the AP.

So how did GM obtain its eye-popping number? The plug-in hybrid Volt can travel for 40 miles using electric battery power before switching to a gasoline engine as it recharges. The 230-mpg estimate comes from an assumption that the majority of drivers would travel in the neighborhood of 50 miles per day.

As the distance traveled rises, the Volt's fuel-efficiency would shrink, as CNN points out: a 300-mile trip would get about 62.5 mpg. (Electric high-speed rail in Europe, by contrast, gets upwards of 300 passenger-miles per gallon for trips of a similar distance.)

In an unwitting illustration of the car's uncertain efficiency, the Washington Post's Green blog headlined one post: "The EPA Gives Could Give the Chevy Volt a 230 MPG Rating. What?"

Regardless of its veracity, the 230-mpg claim gives GM the new marketing tool it craves to help boost its prospects of repaying $50 billion in government loans by 2015. Whether Volt sales will begin sales next year as planned, however, remains to be seen.

In a regulatory update filed last week but caught by Bloomberg, GM admitted that the plug-in hybrid technology "has not yet proven to be commercially viable." GM continued: