DETROIT » The Chevrolet Volt, General Motors’ first foray into mass-market electric vehicles, will get the equivalent of 93 miles per gallon of gasoline in combined city and highway driving while powered by its batteries, the company announced Wednesday.

The compact car, which can go about 35 miles on battery power before a gasoline engine kicks in to generate electricity, will get 37 mpg when running on the generator alone, GM said. In a driving cycle that combines battery and generator power, the car will get 60 mpg, GM said.

The figures, all estimates from the U.S. Environmental Protection Agency, will appear on the Volt’s window sticker when the car goes on sale sometime next month. It’s the EPA’s best effort to come up with a realistic measure of gas mileage for electric cars just as GM and Nissan Motor Co. introduce them to the masses in a few weeks.

GM said last year that the Volt should get the equivalent of 230 miles per gallon in city driving under draft EPA guidelines for calculating electric car mileage, bragging that it could be the first car to break triple digits in gas mileage. But Doug Parks, the Volt’s vehicle line executive for GM, said Wednesday that 230 mpg calculation was based on an early set of assumptions that tried to equate the energy used to recharge the car with gasoline use.

Under the final calculation, the EPA determined the gas mileage for the Volt when it’s on battery power by coming up with a gas mileage equivalent of the amount of electricity it takes to recharge the car. With the Volt it takes 12.9 kilowatt-hours of electricity to recharge the car at 240 volts. The calculation is based on a formula that equates 33.7 kilowatt-hours to use of one gallon of gasoline.

Mileage for the Volt will vary dramatically depending on how much a driver uses the gasoline generator, Parks said. The longer the car is driven, the closer it will get to the 37 mpg figure. But if it’s driven less than 35 or 40 miles per day and is recharged at night, the car would essentially use no gas, he said.

In full electric mode, the Volt is expected to get the equivalent of 95 mpg in the city and 90 on the highway, according to EPA estimates, GM said.

Running on only the gas generator, the Volt is expected to get 35 mpg in the city and 40 on the highway, GM said.

GM says the Volt’s total range on a tank of gas is 379 miles, including the miles traveled on battery power.

GM has been building Volts at a factory that straddles the border of Detroit and the small enclave of Hamtramck, Mich., but hasn’t been able to put them on sale without the EPA mileage sticker. Parks would not say how many had been produced, but said he expects sales to start next month.

"Our expectation, to be based on all of our final checks so to speak, and everything being green, we would ship here in the near future, with our first customers getting vehicles here in December," he said.