It's going to be a small club, but any Gen 1 can do it. I think the criteria should be at least a half tank averaging >40 mpg. It doesn't have to be a >400 mile tank using <10 gallons of gas. It can be a >200 mile tank using 5 gallons of gas.
Any xB1 can do it by driving 100 miles to grandma's & back, by driving in the slow lane with the trucks, and keeping your speed at (or below) 55 mph. You'll average about 45 mpg, & have enough of a mpg cushion to safely get 40 mpg for the tank. Try it the next time you go to the racetrack, an out-of-town concert, etc.
We may have to lower the bar for xB2s. I think 38 mpg is realistic for them, but I'll wait to hear from an xB2 driver or two who actually drive(s) a tank at 55 mph.
Boximurf, you should easily do it with your Scangauge's help.
MrJoshZombie, my best tanks were local country road tanks. I went over 1000 km (624+ miles) averaging 58-60 mpg. Freeway driving brings my mpgs down.