I have noticed twice now a small oil leak where the filter meets up to the block. Its a small trickle, that seems to seep when the motor is under load. Doesn't seem to be leaking when the car is off and sitting, as it sits in the garage often. I have looked the best that i can, and can't see any leaks from the oil lines that go to and from the cooler or any other spots. It will seep enough that oil will collect on the wind detector and pool, causing a small oil spot when the car is moved. I have been using the ford performance oil filter CM-6731-FL820, in place of the normal filter that goes on the boss. been doing this for a while and have not noticed any issues until these last two times. I checked last time to make sure that the old rubber ring wasn't left on the block when changing filters, and also make sure i lube the new rubber with some oil. Not sure what else it may be causing it. I usually hand tighten the filter, then give it a few extra snug ups. Any one notice this or experience this before? Do you think is it may by that the oil isn't warmed up yet and not making a good seal until everything starts to expand?