No, it doesn't come at a price, necessarily. The Otto Cycle engine is most fuel efficient at about 40% of redline. That's not a calculation, and it certainly isn't my calculation. If 3200RPM is about 40%, then 2500 and 3900 will NOT be 40%, and thus BOTH the higher and lower RPMs will be LESS fuel efficient. Where you are confused is that you don't realize that the Otto Cycle engine is most fuel efficient at a certain RPM. You are stuck thinking that you must slow the engine down if you want to save fuel. That is ONLY true if the engine is already running faster than 40%. Or to look at it another way, my own Otto Cycle engine would be rather inefficient (as far as fuel use goes) at 95MPH. If I slow down to 78MPH THEN, I'd be improving fuel efficiency. But if my car is already going 78MPH at the 40% RPM rate, I can't improve fuel efficiency by slowing down. To expect the fuel efficiency to improve at speeds lower than the 40% RPM rate would be expecting an Otto Cycle engine to NOT act like an Otto Cycle engine. I'm not surprised at all to realize that (DUH!) my own engine acts like an Otto Cycle engine. -Dave
