Abstract: A push button combination lock type gas cap and an actuator forming a part thereof, takes the form of a casing which may be mounted to an open end of a fuel tank filling neck with a stopper mounted within the casing for movement between a first position in which the cap is removable from the filler neck, and a second position where the cap is locked thereto. A first center push button mounted on the casing for movement in the direction of its axis between projected and depressed position, shifts the stopper to the first position for locking the cap to the filler tube upon depression thereof. The first push button is maintained in depressed position with a laterally shiftable slide plate operatively engaging the first push button for normally preventing retraction of the first push button absent a selective depression of one or more of a plurality of second push buttons mounted circumferentially about the center push button.