Oil.........
You shouldn't have any oil in it. There are two 1/4" lines. One at the very top of the loop of the tuned pipe that goes to the "tell-tale" connection, to let you know you have a positive water flow and the other, from a lower elbow connection on the tuned pipe, that goes back to the water resonator, which is a diaphragm looking valve with a red plastic cap on it. Look below that cap and you should see two nipples, for hooking up 1/4" lines to. The one to the tuned pipe hooks up to the top fitting, I believe.