A cartridge forming part of a fluid filter includes a filter element, an end cap overlying one end of the filter element, a central tube having one end secured to the end cap, a biasing element, and a relief valve having a valve piston with a head that is biased by the biasing element into engagement with a valve seat formed by an underside of the end cap. The valve seat is configured so that it has a curvature that is larger than that of the head of the valve piston. In the particular arrangement disclosed, a second end cap overlies another end of the filter element, axially opposite the end cap mentioned, and is also secured to the central tube. Preferably, at least one of the central tube and the valve piston defines a depending pilot for supporting an end of the biasing element.
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