What was found
PILOT FLEW 2.2 HOURS ON DRUG SURVEILLANCE FLIGHT. UPON RETURN TO BASE, PILOT NOTED ON POST-FLIGHT, A LARGE PUDDLE OF OIL FORMING ON RAMP UNDER FIREWALL AREA. SUBSEQUENT INVESTIGATION EXPOSED A CRACKED RUBBER 'SEAL' COUPLING BETWEEN OIL FILLER CAP AND OIL TANK. THIS IS HIGH TEMPERATURE/HIGH PRESSURE AREA. CRACK COULD HAVE RESULTED IN TOTAL LOSS OF ENGINE OIL. SUBMITTER STATED PART SHOULD BE TIME-CHANGE ITEM AT APPROXIMATELY 3,000 HOUR INTERVALS. PART CANNOT BE EXAMINED ON PRE-FLIGHT, OR PROPERLY INSPECTED AT 100-HOUR INSPECTIONS.