Filter cartridge

1. A method comprising:

providing a filter cartridge;

the filter cartridge comprising a sump and an inlet/outlet portion extending from one end of the sump having an outside diameter that is smaller than an outside diameter of the sump, the inlet/outlet portion having a cartridge inlet port and a cartridge outlet port;

a first lug on the inlet/outlet portion protruding outwardly from a surface of the inlet/outlet portion in a radial direction perpendicular to a central axis of the filter cartridge;

a shoulder surface that is formed by the intersection of the sump and the inlet/outlet portion;

a filter disposed within the sump;

the first lug comprising a curved surface facing the shoulder surface and curving away from the shoulder surface such that a distance between the curved surface and the shoulder surface varies; and

inserting the inlet/outlet portion into a spool valve manifold;

the spool valve manifold having a valve housing and a valve body positioned within the valve housing, the valve body rotatable about a first axis and configured to receive the inlet/outlet portion in a direction perpendicular to the first axis.

2. The method of claim 1 wherein the curved surface comprises a half-moon shape.

3. The method of claim 1 wherein a minimum distance between the curved surface and the shoulder surface is located in a plane intersecting with the central axis and bisecting the first lug into two halves.

4. The method of claim 3 wherein a slope of the curved surface transitions from a positive slope to a negative slope at the minimum distance.

5. The method of claim 4 wherein the curved surface is symmetrical about the minimum distance.

6. The method of claim 1 comprising rotating the valve body about the first axis from a second rotational position to a first rotational position by moving the filter cartridge thereby allowing a fluid from a fluid supply to flow through the spool valve manifold and into the filter cartridge.