What I understand from this discussion is that when you let off the accelerator pedal on an efi engine the rpm is not being sustained by fuel alone, like it is done on idle, instead the wheels rotation is sustaining the engine rpm. Which means the fuel consumed at 2k rpm while you are not pressing the pedal is less than fuel consumed at 2k rpm with pedal pressed.
As for the original question, whether the car will take more fuel while coasting in neutral or while coasting in gear, it remains unanswered until we know the fuel consumption and distance travelled in both options. We can assume that distance travelled will be higher in neutral but will the gain get offset by the higher idle (engine supported) rpm?
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