periodically, this questions comes up.
so ill give my same answer.
a 100 get 14mpg, uphill, downhill, flat, city, country, or being driven out the back of a c130 one mile up.
15, if you have a 5 speed.
anyone that claims different, has a statistical error.
That's the dumbest crap I've ever heard.
A statistical error? Do you even know what that means?
Anyway, My worst is 12 (when I first got the truck) and my best is just under 16 (all highway, driving 65 the whole time). I don't think I've ever put much more than 21 gallons in mine but I like to not stretch them that far.
I managed just over 300 miles in my FZJ80 with a RTT going to and from Bahia Asuncion a couple years ago, not realizing how far off the highway it was. We coasted into that Pemex on fumes, but that's another story for another day.