As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) IT WAS OBSERVED BY THE ENGINEER THAT THE LEFT ENGINE COWLING AFT OF THE OIL COOLER AIR EXHAUST WAS COVER WITH OIL. THE OIL COOLER WAS PRESSURE TESTED, HOWEVER, A VISUAL LEAK WAS NOT DETECTABLE. THE OIL COOLER WAS REPLACED AND THE OIL ON THE COWLING HAS NOT APPEARED SINCE.