The Chevy Volt’s 230 composite MPG rating was announced Tuesday at GM’s Tech Center in Warren, Mich., during a news conference.

San Francisco ? General Motors said Tuesday its new Chevy Volt will get 230 miles per gallon in the city, dwarfing the current mileage leader and giving the automaker reason to crow about its strides in fuel efficiency.

GM, fresh out of bankruptcy, is looking to the Volt to highlight a parade of 25 new vehicles by 2011 aimed at stemming market-share declines and bringing the automaker back to profitability. The Volt could also give GM a much-needed makeover in terms of its reputation for lagging behind the push toward “green” technology.

Scheduled for late 2010, the Volt will be able to travel up to 40 miles on electricity from a single charge, based on testing of pre-production prototypes, and extend its overall range to 300 miles or more using a flex fuel-powered engine-generator.

The small engine is only used to power the battery.

Actual gas-free mileage will vary depending on the length of travel, the number of passengers, cargo weight and other factors, the company said. The 230 miles per gallon figure is based on tests that used new federal fuel economy standards for plug-in cars.

Fritz Henderson, chief executive of the bailed-out car company, said the Volt is expected to be a “game-changer” for the industry.

“From the data we’ve seen, many Chevy Volt drivers may be able to be in pure electric mode on a daily basis without having to use any gas,” he said.

The competition to push electric technology is heating up, as Ford, Chrysler, Daimler and Toyota are all developing plug-in vehicles. For now, the Volt is taking aim at Toyota’s Prius, which achieves 51 mpg with a $22,000 starting price tag.

The Volt is expected to retail for about $40,000.