Sintered bushings commonly have a porous structure, which under a microscope looks much like a sponge full of small holes. This part may then be impregnated with oil as received. They contain about 18% by volume of oil which is "metered" as required to the surface of the bearing by capillary action when heat or pressure is applied.

With a sintered bronze bushing there is a super shortcut to the commonly recommended overnight soak in oil. Place the bushing on your thumb, open end up. Fill with oil to the top. Put your other thumb on top to seal both ends, and squeeze firmly. In a matter of seconds you will see oil beads on the outside like it was sweating, indicating full saturation of the bronze matrix.