As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
OIL PRESSURE SWITCH USED TO TURN ON FLIGHT TIME RECORDER ('HOBBS" METER) BEGAN TO LEAK OIL FROM ONE ELECTRICAL TERMINAL. A FEW DROPS OF OIL WERE NOTICED WHILE PRE-FLIGHTING FOR A 2-1/2 HOUR RETURN FLIGHT. AFTER RETURNING, THERE WAS A LARGE OIL LEAK. ENGINE WAS 3 QUARTS LOW. TESTING SWITCH INDICATES LARGE OIL LEAK AT ELECTRIC TERMINAL.