Apparently some transmissions still run full pressure though the torque convertor while in neutral, and have the clutches disengaged while your foot is on the brake so savings are slight. Whereas when they are in park lubrication pressure is reduced and the pump is not working as hard. Full lube pressure at neutral is probably good for neutral coasting, but likely won't save you as much at stop lights as putting it in park would. However, if you've been slogging uphill recently at low city speeds and have been surfing the torque convertor, you might be better off leaving it in neutral as the higher lube pressure should give better cooling of the transmission through the tranny cooler.
I remember The RoadWarrior..To understand who he was, you have to go back to another time..the world was powered by the black fuel & the desert sprouted great cities..Gone now, swept away..two mighty warrior tribes went to war & touched off a blaze which engulfed them all. Without fuel, they were nothing..thundering machines sputtered & stopped..Only those mobile enough to scavenge, brutal enough to pillage would survive. The gangs took over the highways, ready to wage war for a tank of juice
It saves a tiny bit. From my scangauge, if I'm in idle-D I can use from 0.20 to 0.22 gallons per hour. If am in idle-N, I go down to 0.14 to 0.17 gph and remember that this lasts for all of 5 to 7 seconds while waiting at a light so don't expect the world in savings. But it's zero effort for minimal gain, so why not?
(turning the engine off for a long light/wait [more than 10 sec] is the better recourse)
I have done that before and noticed that the rpm did drop a little bit whilst in N. I take it to mean saving of a little bit of gas.
When I shift to N at a red light, I leave my hand on the shift knob to remind myself to shift back to D when it is time to go.
I've gotten mild RPM drops and fuel rate drops as reported by ScanGauge in my truck by shifting into N at lights. Every little bit helps. Today I figured out DFCO, and will use that in conjunction with my stoplight strategy in hopes of raising my city mileage in The Beast even more. Currently I'm getting about 14 - 15 MPG city in a truck EPA rated (new ratings) for 12 city.