My current '87 FJ60 gets 16+ MPG on the hiway, 13-14 in town. Numbers are corrected for odo error.
I drive at 100KPH indicated (65MPH true) max cruising speed. Drive like grandma in town.
The truck has only 120K TTAF, 2K SMOH
During the OH it got honed stock bore, polished stock crank, moly rings, oversize stainless valves, port & polish, milled for slight compression bump, desmogged per the diagram in the tech section, carb rebuilt for efficiency, distributor recurved for efficiency, new OEM exhaust, blah, blah
The truck doesn't have the huge FJ62 mirrors, ARB roof rack, winch bumper, etc.
I think it could get another 1-2 MPG w/ a header, but haven't spent the money on that yet. Not 'til something goes wrong w/ the current exh manifold & pipes. It would also help to swap the 31x10.5's for some 235/85R16, but the wheels cost money.