diff: "My Jeep makes all of it's torque at 3k and under, peaks at 3k and drops like a rock over 3200k. Redline at 5k."
That sounded fishy to me, so I looked it up:
http://www.edmunds.com/used/1995/jee...364/specs.html
Edmunds thinks your torque peaks at 4k, not 3k. And the redline is 4750.
"I can still engine brake once up to the right speed, saving even more energy."
Engine braking doesn't save energy, in this scenario. If you build up so much excess speed going downhill that you then have to use engine braking, you've wasted fuel.
"if I pedaled as hard as I could up the hill, and then coasted down"
It doesn't matter when you add momentum to the vehicle. Either way, you're converting chemical energy into other forms (kinetic energy, to the extent that you add speed, and potential energy, to the extent that you add elevation). The only difference between the two strategies is that in your strategy, you create a large differential between downhill speed and uphill speed. The result is that you find yourself going too fast, at the bottom of the hill. A sign of this is that you need to use engine braking. When you do this, you're converting valuable momentum into waste heat inside the engine. That momentum wasn't free; you paid for it. But instead of getting to use it, you're throwing it away.
You could avoid this need to slow down if you use a strategy that doesn't create excess speed in the first place. The result would be the same average speed, but with lower fuel consumption.