My all time best* was 62 mpg on regular. I fueled up, went to work and back, then took a pleasure ride from Carson City, NV, to Folsom, CA and fueled up again in South Lake Tahoe, CA, on the way back. This was with a 2007 Kawasaki Ninja 650. Worst was 3 mpg on JP-8 on multiple convoy missions in Iraq driving an up-armored 1990 International Paystar 5000 hauling 32 cubic meters of gravel in an end dump trailer. Unloaded, that truck got 6. Good thing I wasn't paying for the fuel.

*One time when I was a midshipman I got to ride USS Kamehameha (SSN-642) for a couple days. For a while they let me drive. Despite the boat weighing 8,000 tons and having 15,000 horsepower, I'll bet the amount of 20% enriched uranium I went through on that trip was pretty minuscule. Naval nuclear power for the win!

__________________
Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.