[PaleMelanesian]

I just now found that (thanks Darin!). I have only seen what's here on this thread so I don't know what else is in the book.

Darin is right - the glide is at least half the magic of p&g and leaving it in gear will possibly cost you instead of helping. It depends on how the car handles the in-gear-no-throttle state, but I know that Honda automatics go into heavy engine braking that eats up any potential gains. Neutral is required.

A trip average mpg gauge is hugely beneficial to learning p&g. If you don't have one, it's easy to do it wrong and lose fuel instead of gaining.

I p&g always in a manual. Half the time in an automatic. Even on the highway, even on flat ground. It's work, yes, but it makes the drive more interactive and prevents "highway hypnosis" as well as saving fuel.

Keeping an eye out and adjusting your cycle for other traffic can make your p&g nearly invisible to the rest of traffic. Even in high-speed rush hour traffic, you can do mini-p&g and find good gains without being disruptive.