The invention relates to a method for producing a fuel container and to a fuel container for motor vehicles. The method comprises the extrusion of web-type preforms, the shaping of the preforms in the first heat of the extrudate in a multi-part moulding tool to form shell-shaped intermediate products in a first step, and to form a one-piece, closed container in the same moulding tool in a second step, at least one tank-filling and/or operational venting device being fastened to the inner wall of at least one intermediate product between the first and second steps in such a manner that at least one preassembled part of the tank-filling and/or operational venting device with at least one connection fitting, at least one vent line and at least one functional component is connected to the inner wall by a material and/or form-fitting joint in one work cycle, the wall of the intermediate product being penetrated by the connection fitting during assembly, with the use of at least one conduit section of variable length as a part of the vent line.