As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ENGINE OIL PRESSURE FLUCTUATES AND DOWN TO 0 PSI WHILE REDUCED POWER TO LAND, PILOT SHUTDOWN ENGINE AND LAND SAFELY. FURTHER INVESTIGATION REVEALED OIL PRESSURE LINE REDUCER FITTING ON TURBOCHARGER PRESSURE LINE PLUGGED BY SLUDGE. FITTING CLEANED AND RE-INSTALLED. CALIBRATED GAUGE INSTALLED ON PRESSURE LINE, ENGINE RUN, OIL PRESSURE PARAMETER FOUND IN NORMAL RANGE.