Gen2 Gas Mileage Mystery - Better going over Hill than on Flat !?!

We're not in the generation 5 section by chance...

 

Climbing the hill requires a higher load on the engine. For a gasoline powered one, that means a wider open throttle. More gas burned, but pumping losses are reduced, so that fuel is burned more efficiently. Then there is the coast down the other side. Even if the engine isn't shut down, little fuel is supplied to it then.

This is why pulse and coast can improve fuel economy in any car.

 

It's an estimate.

 

I'm not sure how one would determine the mpg like that with any accuracy. The display gives a number, but I have never found those numbers to be very accurate. For instance, if it says a tank was 45 overall the actual miles and gas added to the tank usually come out more like 42.5 - 43. It is definitely true though that one can almost coast from the top of the pass until where it flattens out past the base of the dam, with just a few brief regions that are uphill. The elevation change is 417 meters at the top to around 50 meters at the 33 and 152 intersection, so 367 meter drop.

I don't go up that grade at 40 mph though, unless stuck behind a truck or other traffic. When the traffic is moving well vehicles will come roaring up on one's butt with closing velocities of 20-30 mph, which is not conducive to a restful drive.