My Neon has a 3spd auto and I tend to P&G only when there is some sort of advantage like a small hill or gradual slope. My area is not very flat so there is usually something to take advantage of and even a small grade will stretch your glide quite a bit. Or if you have a tailwind, P&G will pay off quite a bit.
If its truly flat then try both P&G and 45mph for a tank each and see what does better.
Ian
__________________
|