As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) PILOT REPORTED LOW OIL PRESSURE DURING DESCENT WITH ENGINE RPM REDUCED TO IDLE. COMPLEATED OIL PRESSURE GUAUGE CALIBRATION CHART USING CABIBRATED GAUGE. INDICATED 30PSI -> ACTUAL 38PSI, INDICATED 20 -> ACTUAL 27PSI, INDICATED 15PSI -> ACTUAL 20PSI, INDICATED TOP OF RED LINE 12PSI -> ACTUAL 18PSI, MIDDLE OR REDLINE 10PSI -> ACTUAL 16PSI. (TC NR 20070803015)