Fuel-dispensing nozzle inhibitor

A nozzle inhibitor is positioned in a filler neck closure assembly between a pivotable outer door and a pivotable inner door to prevent a user from pumping unleaded fuel into a diesel fuel tank. The nozzle inhibitor blocks full insertion of a small-diameter unleaded fuel nozzle into the filler neck closure assembly yet allows full insertion of a large-diameter diesel fuel nozzle into the filler neck closure assembly.