I have the worlds most irritating oil leak. After an hour or two of flying there will be 2 drops of oil right under where you drain the oil, which, I guess is about dead center under the engine. I'd say about a drop an hour. I have replaced the valve cover gaskets with the silicon type and Had a leak from the "oil dip stick holder plastic tube thing" working itself loose. Now I can find no evidence of an oil leak other than a drop in the middle of the cowling every once in a while. Ideas? At annual all hoses were replaced and I suspected a leak in the oil cooler hoses but the engine and hoses are clean enough to eat off of and no evicence of oil anywhere. Is it possible that the drain could leak only while the engine is running?