My engine is a 912ULS with 1100 hours. I personally put the last 750 hours on it and it has not been abused. Oil, and filter are changed at 50 hrs, plugs at 100, auto fuel only. On the last 2 leak down tests cylinder 3 was low 73/80. Those tests the engine was cold for the test so I ran the engine and retested it immediately and got 78/80. Today at 100 hr check I came in from a flight and tested within 15 minutes of shutdown and am again getting 73/80 on #3. My second problem possibly related is oil usage about 1/2 -3/4 oz per hour. The engine seems to run fine makes good power and gets very good mileage. The engine is extremely clean so it's not leaking and the plugs all look good. I would expect #3 plug to look different if oil was being used in that cylinder. What action should I take?