I just changed the oil, so I decided to observe for this thread specifically. I added oil to the top, then started Vader up and observed NOTHING in the site tube. I added the rest, one bit at a time till I as at the max line. Started, and the oil level beside hiccuping some air bubbles didn't budge. It stayed at the max line and never "filled". I'm under the impression that only during load will the site tube be totally filled, and in my opinion not necessarily ever flowing oil through the tube.