Filter system for a liquid medium to be filtered, in particular for fuel or oil, in particular for lubricating oil, in particular for the internal combustion engine of a motor vehicle, comprising: - a filter head having a bottom-sided drainage channel for the fluid and having a stop element; - a filter designed as replaceable filter cartridge, comprising a filter element disposed in a housing of the replaceable filter cartridge, wherein the replaceable filter cartridge is mountable on the filter head by means of a screwing-in movement oriented around its longitudinal axis, wherein the replaceable filter cartridge features at one end a supporting ring, which is rotatably attached to the housing component, in particular to the cover (46, 48) of the housing component, of the replaceable filter cartridge relative to the longitudinal axis of the replaceable filter cartridge, wherein the supporting ring features an eccentrically disposed closure member for the drainage channel and a first positioning means, which can be guided against the stop element of the filter head by means of the screwing-in movement in order to position the supporting ring relative to the filter head in a predetermined rotating position with the closure member axially aligned with respect to the drainage channel, so that the closure member is transferable by means of an axial movement of the filter derived from the screwing-in movement into its sealing seat on the filter head closing the drainage channel, characterized in that the supporting ring features a second positioning means for contacting the stop element by means of which the supporting ring is held in a rotationally fixed manner on the filter head during an unscrewing movement of the filter in the direction opposite to the screwing-in movement for releasing the closure member from its sealing seat, so that the closure member can be moved out alone in the axial direction of its sealing seat, wherein the two positioning means (24, 26) are web-shaped. - a filter head having a bottom-sided drainage channel for the fluid and having a stop element; - a filter designed as replaceable filter cartridge, comprising a filter element disposed in a housing of the replaceable filter cartridge, wherein the replaceable filter cartridge is mountable on the filter head by means of a screwing-in movement oriented around its longitudinal axis, wherein the replaceable filter cartridge features at one end a supporting ring, which is rotatably attached to the housing component, in particular to the cover (46, 48) of the housing component, of the replaceable filter cartridge relative to the longitudinal axis of the replaceable filter cartridge, wherein the supporting ring features an eccentrically disposed closure member for the drainage channel and a first positioning means, which can be guided against the stop element of the filter head by means of the screwing-in movement in order to position the supporting ring relative to the filter head in a predetermined rotating position with the closure member axially aligned with respect to the drainage channel, so that the closure member is transferable by means of an axial movement of the filter derived from the screwing-in movement into its sealing seat on the filter head closing the drainage channel,