It's a bit hard to understand where you're trying to go here but assuming that you state it doesn't take fuel to "counter engine braking", you're wrong. Engine

It's a bit hard to understand where you're trying to go here but assuming that you state it doesn't take fuel to "counter engine braking", you're wrong. Engine braking is just that, using the engine as a brake. If no fuel is added, pumping losses will make it act as a (relatively weak) brake. If you want to coast without braking, with the clutch engaged, you will need to inject fuel to counter the pumping losses of the engine, losses which are higher if the engine is not idle. Losses in the power train add to the braking effect, which must further be counted with additional fuel. If you're going downhill with clutch disengaged and maintaining your speed, engaging the clutch will very likely increase your fuel consumption for the same task (maintaining speed). Automatics have a coasting gear (usually the last or only overdrive gear) for this very reason. (Sorry, I had to do that.) Side notes: 1. Coasting is not braking. People seem to be mixing "coasting to a stop" and "coasting" in general. Engine braking, when your intention is to reduce your speed, is more efficient than friction brakes, but coasting does not mean that you intend to reduce your speed. 2. Who drives a car with a 2-stroke petrol engine? :)