As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING CLIMB, THE ENGINE OIL PRESSURE WAS LOST. THE PILOT PULLED BACK ON THE THROTTLE AND THE PRESSURE CAME BACK TO NORMAL. ELECTED TO RETURN TO DEPARTURE WHERE AN UNEVENTFUL LANDING WAS MADE. DURING TAXI, BLACK SMOKE WAS SEEN COMING OUT OF THE ENGINE. TROUBLESHOOTING FOUND THE OIL PRESSURE TO NR 4 BEARING TO BE EXCESSIVE THE WILL BE REMOVED AND SENT FOR REPAIRS.