Abstract: A gas cap for sealing a gas tank adapted to be permanently mounted on a vehicle and a combination of gas cap and fender device for connecting the gas cap to the vehicle, the gas cap being attached to an access plate having a contoured recess hingably attached to a fender of the vehicle pivotal between a closed position and an open position containing a gas tank with a filler tube extending from the tank and attached to the fender wherein the filler tube includes a neck member provided with a threaded fitting and a gas cap comprising a cap of disk shaped construction with a transverse handle member for pivotal rotation, a cylindrical journal member, longitudinally slideable between an inner sealing position and an outer disengaged position, a sleeve, a threading device provided on the closure means for engaging the neck member and a retaining device adapted for preventing the removal the gas cap from the access plate providing a permanent connection to the vehicle.