Abstract: A tank closure, especially for a tank of a motor vehicle, with a bayonet cap having a pair of tension clamps. The tension clamps, during a rotation of the cap, are axially displaceable through the bayonet-type thread at the tank neck and are urged against the thread by a helical compression spring. The spring rests on a bracket of a closing pipe guided in a housing of the cap and joined thereto so that the spring urges the closing pipe, especially a flange associated therewith and covered with a sealing ring of rubber or the like, elastically resilient material onto an annular sealing surface of the tank neck. A self-lubricating synthetic resin spacer sleeve, that is, a sleeve which readily slides on metal, is inserted between the flange of the closing pipe and the pair of tension clamps.