When the Volt calculates its fictional MPG, does it use 33.7kw = 1 gallon of gasoline for the electric portion?
EDIT: To my knowledge, the only car which truly operates as a series hybrid most of the time is the 2nd gen Accord Hybrid. It has no gearbox. The engine can drive the gears at a single fixed ratio on the highway, but otherwise it truly operates as a generator only: