As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT TOP OF CLIMB, NR 1 ENGINE OIL PRESSURE STARTED DROPPING OFF INTO CAUTIONARY RANGE. RAN ABNORMAL CHECK LIST, REDUCED POWER TO IDLE. OIL PRESSURE DROPPED BELOW RED LINE, SECURED ENGINE AND RETURNED FOR LANDING. REPLACED NR 1 ENGINE OIL PRESSURE TRANSMITTER IAW DC8 MM 79-30-33. OPS CHECK GOOD ON ENGINE RUN.