[Big Dave]

High altitude would be good for fuel economy except for one thing: uphill grades.

Most high altitude terrain I've ever seen is either uphill or downhill, rarely flat.

Remember you road load equation: 20 lb load per ton per percent grade. Entropy assures you never recover all your potential energy coming downhill.


BTW, a 6.2 GM diesel (mine) made it to Leadville and over every pass I tried. I even got the thing to the summit of Pike's Peak - Altitude 14,406 ft.

Caveat: I did have to slow down and it smoked like a steam locomotive.