A gas tank hole can be because a number of causes. If your car has undercoating installed – undercoat is a paraffin-based spray-on coating that likes to grab and hold salt and other metal-eating chemicals – rust-out holes are possible. Or, if your car hits a large rock or pothole, you run the risk of a gas tank hole. It’s also possible the tank hanger assembly could break, causing the tank to drag on the ground, forming a hole. If you take your vehicle off-road and there’s just not enough clearance, it’s possible that you will find a hole in your gas tank. The bottom line is, wherever you drive, be careful because gas tank holes are serious business.
For more info, see How to Repair a Gas Tank With a Hole In It