Good points, but diesel's higher MPG doesn't have to do with the difference in energy density but in cycle efficiency. The Diesel cycle is, all things equal, i

Good points, but diesel's higher MPG doesn't have to do with the difference in energy density but in cycle efficiency. The Diesel cycle is, all things equal, inherently less efficient than the Otto cycle. Hoever, since it allows much higher compression ratio it's efficiency ends up being very high (20 vs. 30 traditionally) [see Faires]