Let's assume we have a generic, standard design ICE car, except that transmission is CVT (continously variable) and can be popped into neutral, since this simplifies the problem. Assume car travels in a hypothetically-empty freeway at any speed and also assume that driver is optimizing fuel consumption only, not time-to-destination or any other parameter. I think that to optimize fuel, driver should do the following: Starting from point A, accelerate while keeping engine RPM optimized for fuel engine efficiency to some maximum speed -- not so high as to cause excessive air resistance. At this maximum speed, the car is put into "neutral", essentially coast to zero speed, re-engage transmission and repeat the process until driver gets to point B. Let's assume that engine remains idling during coast phase, not turned off (although I don't think it affects conclusion). Instinctively one might think it better to leave car at some constant, "optimum" speed (i.e., leave in cruise control) but I assume that coasting is better since it reduces the friction of the engine/transmission during coasting phase. Is this logic correct? I realize this is overly simplified, but that is my intention. If so, how does driver choose the maximum speed before coasting?