Fuel tank for a vehicle comprising a filler neck for receiving a diesel fuel filler nozzle

The fuel tank has a filling connection (1) sized for reception of a large-diameter filling gun (2) for supplying diesel fuel. The filling connection contains a blocking valve (3). The blocking valve prevents filling of the fuel tank upon insertion of a filling gun of lesser diameter and is opened only by insertion of the large-diameter filling gun, to provide a connection between the filling connection and the interior of the fuel tank.