Misfuel inhibiting device for a fuel inlet pipe of a vehicle tank

This device (1) comprises a casing (2) delimiting an opening (24), a flap (26) movable between a closed position and an open position in which the closing flap releases a passage through the opening (24) to allow insertion of a fuel dispensing nozzle of a predetermined diameter, and locking means movable between an unlocking position and a locking position of the flap (26) in the closed position. The device (1) also comprises a driving element (32) rotatable, designed to drive the locking means to the unlocking or locking position, an elastically deformable element (34) delimiting an opening (36) of cross-section smaller than the diameter of the nozzle, so that insertion of the nozzle through the passage opening (36) causes radial deformation of the element (34), and means for converting the radial deformation of the element (34) into a rotation of a predetermined angle of the element (32).