I believe more energy was lost in the automatic because of slippage and complexity, and also the shift points were not always optimized for fuel efficiency. I'm under the impression that computerization has pretty much solved these problems. Humans can no longer shift as intelligently as the new automatics. At least that's what I've heard. Not only that, automatics used to have fewer gears than manuals, and that's not true any more, either. I rented a Kia Soul with a 7-speed automatic.