Maybe a couple of gallons at most. NOT 5 gallons as someone mentioned above. Your whole tank only holds 15.5 gallons. 5 gallons would be a full 1/3 tank left. Don't want to run out of gas and take a chance you'll suck some sediment from the bottom of the tank through your fuel system.

 

I think I have about 3 gal left if the light goes on & I fill it up it takes about 12 1/2 gal