I totally concur with Walter's logic. It's the exact logic I utilize.Ah. That's a somewhat different question. The general consensus is to use the ICE for part of the freeway portion. It's likely a little better for efficiency without the start/stop cycles of the lower speed parts, but mostly it's a lot more pleasant - at 60 you'll only know the engine is on from the instruments, but in stop and go you'll feel and hear the engine.