In my old 91 3.0 (had manual, 4.56's and 31" tires) I got about 17-18.
I still kick myself for rebuilding that motor rather than swap a 5VZ (3.4)...
My Taco Doublecab longbed gets about 17-18. I blame the ethanol they are putting into gasoline now.
Then again, I have almost twice the HP...