It is recommended that you use 90W gear oil in it, a larger-than-grease nipple was fitted to some of the early cars, then not put in 'cause folks mistook it for a grease nipple. It would be in the center of the cover over the pinion gear. If it isn't there you could add oil by removing the cover: Be aware there may be shims there, and pull out the "puck," spring and insert to allow you to pour it in. Not certain how much it should have, the manual says "several strokes of an 'oilgun'."