If you're coming to a stop or trying to maintain your speed down a steep slope, keep it in gear. If you're trying to maximize the distance traveled without accelerating, pop it in neutral. Whether or not the engine is idling in neutral or in DFCO makes very little difference in your overall FE. The point is to always cover the maximum distance or anticipate your next move. I wouldn't put an automatic transmission in neutral while the car is still rolling to save fuel.

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CENSORED due to not family friendly words