I agree, cruise control on a very flat road will most likely produce better results than your foot.

On the coasting issue, if the gas engine is running, then you're still using gas in all 4 cylinders to keep the engine running while you're coasting, using more gas than just using 1, and letting the inertia of the car help turn the engine. That's what I was referring to, not shutting of the gas engine completely and coasting.