writes "General Motors, emerging from bankruptcy, today announced that its upcoming plug-in hybrid vehicle, the Volt, will have an EPA-rated 230 mpg for city driving (approx 1L / 100km). The unprecedented rating is the result of a new (draft) methodology for calculating the "gas" mileage for vehicles that operate primarily or extensively on electricity. The Volt, due out late this year, can drive approximately 40 miles on its Li-Ion battery pack, after which a gasoline engine kicks in to provide additional electricity to turn the wheels. Running off the gasoline engine yields approximately 50 mpg. Of course, the devil's in the details, because the conversion of grid-based electricity to gasoline-mileage is imprecise."