Whenever you fill your car with gas, you first must open the fuel door covering the gas cap. The fuel door is attached to the side of the car with a hinge. Since this hinge is exposed to rain, cold, snow and many other weather elements, it may begin to rust and deteriorate. Call your local car dealer or auto repair shop to find out if they have a replacement hinge for your particular make and model of car. Removing the old hinge and replacing it is something you can do yourself. Each make and model of car may have slightly different hinges and mounting techniques, but most have similar components.
Open the fuel door as wide as it can go. Place a screwdriver through the metal loop in the inside center of the fuel door. Pull the handle of the screwdriver toward you to pry the hinge tabs out of the holes on the side of the car.
Lay the fuel door flat on the ground, with the outside of the door facing down. With the screwdriver still inserted in the metal ring, use it as leverage to pull the metal ring's tabs out of the slots on either side. Set the metal ring aside.
Place the tip of a flat-head screwdriver underneath one of the tabs on the side of the hinge. Push the tab up to release it from the fuel door. Repeat with the second tab. Slide the old hinge off the fuel door and set it aside.
Line up the two large tabs on the bottom of the hinge with the openings on the back of the fuel door. Push the tabs into the openings until the hinge locks into place.
Place one end of the new metal ring into the slot in the center of the hinge. Pull the ring over the center of the hinge and push it down so that the other end of the ring slips into the slot on the other side of the hinge.
Remove any broken off tabs from the hinge holes in the side of the car. Lift the fuel door up to the opening in the side of the car. Line up the tabs on the side of the hinge with the two small holes in the side of the opening. Push the new hinge firmly into place. Open and close the fuel door a few times.