[PaleMelanesian]

Oh I understand DFCO very well. It uses zero fuel. But it's not always the best approach to making mpg. It also eats up a lot of momentum. I burned fuel to make that momentum. I want it to take me as far as it can. DFCO adds an unacceptable amount of drag.

Yes, I'm in and out of N and D all the time. Back and forth and back and forth. At least on a Honda automatic (my personal experience), that's the way to get the best mileage.

Yes, while slowing for a turn or a stop, DFCO is useful as you're slowing AND not using gas. But you could start neutral coasting sooner and you don't have excess speed to burn off. You spent unnecessary fuel to be in that position, so DFCO is only a least-bad solution. Better to not need any braking at all.