[QUOTE] The real reason her car is more efficient than mine has nothing to do with batteries or electric motors but is the direct result of the computer control system and an advanced gasoline engine.[/QUOTE] Huh? I recall an SAE sponsored talk from a Honda VP who said that the Insight got about a third of its mpg benefit from each of: lightweighting, engine downsizing and efficiency improvements, regen braking. The battery/motor is directly responsible for the latter. How will you do regen without a motor/generator? The hybridization enables the engine downsizing, ie it allows you to maintain acceptable acceleration with a smaller engine. And the hybridization allows you power management advantages, ie you can run the engine in more efficient ranges. Sourcing/sinking to the batteries allows this. The Prius is not light like the Insight. And it has a much larger battery. Thus much more of its mpg benefit is directly due to hybridization.