Filter for cleaning lubricating oil

Oil filter for the cleaning of lubricating oil, comprising:

• a filter case which in the installed state is disposed at least approximately upright, an annular oil filter cartridge inserted in the case, the filter case including an oil inlet leading to an inlet chamber for flowing contaminated oil around the oil filter cartridge and including an oil outlet for clean oil connected to an interior chamber of the filter case which is an interior portion of the oil filter cartridge, the oil inlet and outlet being in a base at the bottom end of the filter case, the filter case including a drain passage at the bottom end of the filter case, and which is isolated from the oil outlet and which, by removal of the oil filter cartridge, is connectable to the inlet chamber of the filter case, and the drain passage having an axial direction and having a closure which closes the drain passage off from the filter case, the closure being a valve body having a head portion and being displaceable in the axial direction in the drain passage, the drain passage having at least one constriction which forms a valve together with the head portion of the valve body for directly controlling the drain passage, a first weaker spring located on one side of the head portion for biasing the valve body in an opening direction, and a second, stronger spring located between an end face of the oil filter cartridge and the opposite side of the head portion for biasing the valve body in a closing direction, the second, stronger spring thrusting, when the filter cartridge having an end face facing the valve body is inserted into the filter case, against and directly contacting the end face of the oil filter cartridge facing the valve body.