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There's nothing quite so aggravating as an oil leak. I had one on an experimental plane I own.....not my Mooney, but since it's got a Lycoming, my travails might be of general interest to Mooney owners and something to check for on your annuals. About a year ago, I began to have a small, but persistent oil leak. I looked in all the suspect places and did a thousand things none of which solved the problem. Like all oil leaks, this one did not fix itself and went from a minor irritation to a major concern. There's a picture of the post flight when I decided that the plane was grounded until fixed...the leak had gone from "progressively worse" to major issue in one flight. Grounded! The oil was coming from "all over" which made trouble shooting difficult. Even a quick run-up after a thorough bath wouldn't localize the leak to anything better than "left side forward of the accessory section". It actually looked like it was somehow coming from the starter. I did find the leak and it wasn't tough after the leak got big enough. A hole in the top of #2 cylinder rocker-arm oil return line. Because I was paying close attention to oil consumption, I can say that on that last flight, it was losing about a pint in 15 minutes. Good thing I wasn't on a long flight! Good thing I wasn't running minimal oil quantity. What caused the hole was also of interest. Even though there was nothing rubbing on any of these lines when I repeatedly checked them statically, it is now apparent that when the engine was running, the baffeling just above the line would "bow out" just a bit and make contact with the line. The baffeling edge, over time with engine/airstream vibration, sawed a nice cut into the soft aluminum.