the 40mpg is ok, but again this is aimed at commuters that don't need a ton of miles everyday. the car will have a 600 mile range from the posts I have read. the first 40 is just on batteries then the small gas engine creates electricity to run the car until its out of gas. The gas engine does not drive the wheels, just creates electricity.

Estimated fuel economy @ constant state of charge:
50 mpg during charge sustaining operation

Daily usage equivalent mpg:
@ 40 miles or less:
not applicable – no fuel used

@ 60 miles:
150 mpg

@ 80 miles:
100 mpg

0 to 60 miles per hour:
8 to 8.5 seconds

Top speed (miles per hour)
120 (limited duration)

from the GM-Volt Site. Not too shabby in my opinion. Considering my commute is about 10 miles round trip plus maybe 20 miles during the day (Realtor).
http://gm-volt.com/full-specifications/

 

"Edmunds Inside Line stirred up kind of a hornets nest yesterday when they made the claim the Chevy Volt won't use the engine to recharge the battery. Turns out they weren't exactly right. GM's VP for Global Program Management, John Lauckner, rebuffed Edmunds' claims and stated, in no uncertain terms, that the engine can recharge the battery, but recharging the battery is not its objective. Engines are most efficient when operated at a steady state — tons of tricks can be implemented to optimize performance at a constant RPM, and that's the plan for the Volt.

As with any steady-state output, sometimes there will be surpluses. Those surpluses of electricity not used by the electric motor, as might occur during light loads, will be dumped into the battery so that energy isn't wasted. But recharging the battery is not the objective of running the engine. In addition to extra electricity from the engine/generator, energy reclaimed from regenerative braking will also be stored in the battery. Over an extended period of these surpluses being added to the battery, it's possible for the engine to switch off and the car to return to all-EV mode for an unspecified distance." [EdmundsInsideLine]