[comptiger5000]

In higher powered, overgeared vehicles, powering up the hill is better, as it keeps the engine closer to its sweet-spot. In the case of my Jeep, I get my best highway mpg by maintaining steady speed up a hill, and then coasting down the backside, provided it's not steep enough for me to gain speed on the descent.

The mpg achieved from that is certainly better than what I see on flat ground, or very long, steep hills (where slowing down at the top doesn't prevent me from getting above my cruise speed by the bottom).