Lots of forums will tell you that the 15 gallon and 20 gallon Jeep gas tanks are the same tank with different filler hoses, but is it really as simple as cutting a hose to get a higher capacity? Yup! We will take a look inside the tank to see exactly how to fit a few more gallons into it. I can't take all the credit @unofficialuseonly taught me this trick.
This Jeep is a 1994 YJ I cannot guarantee that this works on other models of Jeeps or even other years of YJ.