Another bingo.... but perhaps it varies widely depending on load, terrain, driving habits, etc.
If one is hotdogging in mountainous territory, it'll burn more fuel. I have no interest in that.
I'll haul some load -- even for going downtown, I'll carry an extra 10 lbs (more coming back).
And if it's a week away from base camp, it'll be closer to 150 lbs.
But I'll be ... riding? ... driving? ... like I would on an Interstate highway.
Responsibly at a speed suitable for the terrain and trail.
Why, I could even get 30 mpg. It's a testable hypothesis.