The invention relates to a liquid filter, especially an oil filter, for cleaning lubricating oil, especially for internal combustion engines of automobiles, comprising an upright filter housing which contains a receiving area for a ring-shaped filter insert that is inserted into said receiving area, an inlet channel for unclean liquid, an outlet for clean liquid, and an additional discharge channel which is exposed when the ring-shaped filter insert is removed. An eccentrically projecting pin is moulded to a lower end plate and sealingly penetrates an opening of the discharge channel when the ring-shaped filter insert is introduced into the filter housing. According to the invention, a ramp is configured on the floor of the receiving area and is positioned in such a way that when the ring-shaped filter insert is introduced into the filter housing, the pin lies on said ramp and when the ring-shaped filter insert is rotated about its longitudinal axis, the pin slides downwards along the ramp and enters the opening of the discharge channel at the lower end of the ramp. This improves handling.