[Nevin]

If you are able (like on interstate or something) it helps if you accelerate downhill, and then coast more uphill.

Slowly accelerating downhill won't use any more fuel than driving a constant speed on a flat spot, and then the coasting uphill will certainly save you a lot.

On long trips I hardly ever use my cruise unless it is mostly flat roads. Uphill/downhill you can always beat cruise for mileage IF you do it right.

On a 2000 mile round trip last summer I actually got my best mileage driving in the mountains. Everywhere else I could only get about 27 MAYBE 28, but with the cruise off averaging speeds of 80-85 mph, I got a solid 30 mpg. in the mountains.

Cruise does not help you get better mileage, it is just for when you feel like being lazy.