A fluid management tool for introducing fluids into a casing string incorporates a mud saver valve configured to open and allow fluid flow in response to fluid flow pressure reaching a predetermined opening pressure, and will automatically close when fluid flow pressure is reduced to or below a predetermined closure pressure, thereby preventing fluid spillage when the tool is withdrawn from the casing. The mud saver valve includes a mud saver spool having a slotted spool cage and being axially movable within a longitudinal bore in the main body of the tool, between an upper or open position in which fluid can flow out of the spool cage and into a discharge bore at the lower end of the main body, and a lower or closed position in which the lower end is seated against the exit bore to prevent flow therethrough. A check valve may be incorporated into the lower end of the mud saver spool. The fluid management tool also may incorporate a main seal and air bleed valve subassembly and a secondary suction seal and check valve subassembly.