As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, RIGHT ENGINE OIL PRESSURE FLUCTUATED AND WENT TO ZERO. RETURNED TO SAN. AFTER LANDING SHUT DOWN ENGINE. CLEANED RIGHT ENGINE AND FOUND OIL CAP HALF OFF. SERVICED RIGHT ENGINE WITH 2.5 GALLONS. RAN ENGINE, NO LEAKS NOTED. NO PRESSURE FLUCTUATIONS. REPLACED OIL CAP AS PRECAUTION.