OK I'll chime in...20 to 24 mpg before any mods w/o a roof rack, avarage to aggresive driving...
20" rims with BFG tires, 3" lift All Pro Lift bumpers and rails, Gobi low pro roof rack with lights, TRD CAI...brought it to 18 to 20 mpg, 210 to 220 miles before
gas light comes on...
Then the big INSTALL;
when I'm nice and flow with traffic I get 17 to 19 mpg (also when towing my 2 jet skiis)...
when I'm nasty and my right foot gets on the heavy side (or when I wanna off road on three wheels) my worst is 10 mpg to an avarage of 15 mpg...
I'm happy with the realization of the FJ as my TOY and it really dosen't matter anymore what I get...what does matter is...HOW MUCH FUN I'm having
while get'n what I'm get'n

!
Like others have said...if I want more MPG...I'll get a Prius or other kind of Hybrid...good luck 'n have fun!