[sheepdog 44]

Don't shift into nuetral in an automatic it's never worth it. Please don't even try to do it you'll thank yourself later.

P&G in gear will only be beneficial if you can turn the engine off while your coasting in gear which is one thing. In gear your coast will never be as long as if you were in nuetral. The length of your coast in relation to the length of the pulse will be a good indicator if it'll be worth it. But if you cant turn off the engine in your coast your gains will be marginal if not worse.

What I think your getting at is driving with load, which is the best thing you can do in an automatic. Accelerate downhills, lightly coast in gear at the bottom flat slowly killing your speed to the target cruise mph. If you have to accelerate do it before a hill or cruise at a higher speed in anticipation. Never accelerate uphill! Drive slower. Accelerate less to a lower speed and cruise at the slowest speed in the highest gear you can get the AT into. Pump up your tires.

Those are good gains to be had by simply driving with load. My old Saab did 26mpg normal driving, I got it up to 30mpg by changing the nut behind the wheel.

Just my opinion.

For Manual cars P&G is always better. Not every car has the luxury of leanburn, and in the case where your car doesnt leanburn (which is the vast majority,) your gains will be even greater than maintaining speed.