After filling my 18.5 gal. tank in my 01 ,4x4, extended cab, 2.7 step side , SR5
Tacoma having 31.5" tires and carrying an extra #400 in tool box and tools this is the gas mileage I ended up with after a week of on and off road driving in these WV mountains.
After filling the tank I used 16 gallons even and drove 300 miles = 300 divided by 16 = 18.75 mpg.That leaves 2.5 gal. in the tank and that means that I should get about 346.875 gal. per tank. (I do not intend to let it run out).
The warning gas light came on at 284 miles so I should have had about 52.575 miles to go before running out after the warning light came on.
I'm not at all unhappy with this mileage and if I got rid of some of the tools and slowed down a little I'm sure I could get better mileage. If you allow for the over sized tires I probably get even better gas mileage than I figured here.
Mike