GREENER FUEL EFFICIENCY
For trips less than about 40 miles (64 km) per charging cycle, the Volt will not use any onboard gasoline engine or possibly a fuel cell system powered by hydrogen. Either way, either plug-in auxiliary electricity source will be a lot greener than standard petroleum.
What's really cool about the GM Chevy Volt is that a gasoline engine can be optimized to run at its most efficient level to maximize the production of generating electricity and significantly reducing emissions at the tail pipe. Cars get their worst gas mileage in slow speeds, and are optimimum at 55 m.p.h. Now an engine can run at its most efficient output and that means less bad carbon dumped into the environment.