reply to Jeff:
How much exactly do the lower air temps at night help cool powerplants? As far as I know, most powerplants are water-cooled, and I would assume that these bodies of water would be large enough to mostly damp out the temperature transients created by warm days/cold nights. (I'm not studied up on lake/river temperature variations, so this could be off)

response to those calling the Volt a hoax:
This is the single-most exciting project in the auto industry right now, and many of the best engineers have applied to work on this vehicle (from GM as well as other companies). From what I know, GM has quite an investment in the Volt (including advertising/branding), to not come through on this vehicle would be a tremendous waste of resources.