Diesel is where it's at. A little over a year ago, I bought a 2008 Ram 3500 with the 6.7 Cummins that's deleted, tuned, and lifted on 35s. I know the on-board fuel mileage calculator isn't going to be 100% accurate, but even if I knock a little off, I'm still getting excellent fuel mileage while driving around, plus I have the added benefit of being able to pull a house of its foundation if I wanted to.
Also, if this guy really invented a diesel engine that gets over 100mpg, we'll find him floating face down in a river somewhere before too long.