A fuel tank filler apparatus adapted for use in a vehicle fuel system, the fuel tank filler apparatus comprising a blow-molded fuel-tank filler neck associated with a fuel tank, the blow-molded fuel-tank filler neck shaped to extend around a central axis of the fuel tank filler apparatus to define a fuel receiving passageway and the blow-molded fuel-tank filler neck including an outer end having a top surface that defines a mouth that opens into the fuel receiving passageway, a capless filler neck closure adapted to be mated with the outer end of the blow-molded fuel-tank filler neck to block fuel and fuel vapor from escaping the blow-molded fuel-tank filler neck during use of the fuel tank filler apparatus, the capless filler neck closure including a nozzle-insertion housing that extends into the blow-molded fuel-tank filler neck, an outer dust cover mounted to pivot relative to the nozzle-insertion housing from a closed position arranged to block dust from entering the nozzle-insertion passageway to an open position arranged to allow a fuel nozzle to enter the nozzle-insertion passageway, and an inner closure door spaced apart from the outer dust cover along the central axis and mounted to pivot relative to the nozzle-insertion housing from a closed position arranged to block fuel and fuel vapor from escaping the associated fuel tank and an open position arranged to allow a fuel nozzle to enter fuel receiving passageway, and interface means for pushing a portion of the blow-molded fuel-tank filler neck into a round shape in order to facilitate receipt of the capless filler neck closure in the blow-molded fuel-tank filler neck and for coupling the capless filler neck closure to the blow-molded fuel-tank filler neck without welds or permanent attachment to facilitate selective decoupling of the capless filler neck closure from the blow-molded fuel-tank filler neck thereby allowing non-destructive removal of the capless filler neck closure for replacement or repair of the capless filler neck closure, characterised in that the interface means includes the interface sleeve including an inner wall that defines a closure-receiving space that receives the nozzle-insertion housing of the capless filler neck closure and the outer wall that is spaced apart radially from the inner wall and wherein the outer wall of the interface sleeve is formed to include a crimp tab and the blow-molded fuel-tank filler neck is formed to include a tab receiver and the crimp tab extends into the tab receiver to couple the interface sleeve to the blow-molded fuel-tank filler neck. a blow-molded fuel-tank filler neck associated with a fuel tank, the blow-molded fuel-tank filler neck shaped to extend around a central axis of the fuel tank filler apparatus to define a fuel receiving passageway and the blow-molded fuel-tank filler neck including an outer end having a top surface that defines a mouth that opens into the fuel receiving passageway, a capless filler neck closure adapted to be mated with the outer end of the blow-molded fuel-tank filler neck to block fuel and fuel vapor from escaping the blow-molded fuel-tank filler neck during use of the fuel tank filler apparatus, the capless filler neck closure including a nozzle-insertion housing that extends into the blow-molded fuel-tank filler neck, an outer dust cover mounted to pivot relative to the nozzle-insertion housing from a closed position arranged to block dust from entering the nozzle-insertion passageway to an open position arranged to allow a fuel nozzle to enter the nozzle-insertion passageway, and an inner closure door spaced apart from the outer dust cover along the central axis and mounted to pivot relative to the nozzle-insertion housing from a closed position arranged to block fuel and fuel vapor from escaping the associated fuel tank and an open position arranged to allow a fuel nozzle to enter fuel receiving passageway, and interface means for pushing a portion of the blow-molded fuel-tank filler neck into a round shape in order to facilitate receipt of the capless filler neck closure in the blow-molded fuel-tank filler neck and for coupling the capless filler neck closure to the blow-molded fuel-tank filler neck without welds or permanent attachment to facilitate selective decoupling of the capless filler neck closure from the blow-molded fuel-tank filler neck thereby allowing non-destructive removal of the capless filler neck closure for replacement or repair of the capless filler neck closure, characterised in that the interface means includes the interface sleeve including an inner wall that defines a closure-receiving space that receives the nozzle-insertion housing of the capless filler neck closure and the outer wall that is spaced apart radially from the inner wall and wherein the outer wall of the interface sleeve is formed to include a crimp tab and the blow-molded fuel-tank filler neck is formed to include a tab receiver and the crimp tab extends into the tab receiver to couple the interface sleeve to the blow-molded fuel-tank filler neck.