As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) PILOTS REPORTED OIL PRESSURE WAS BELOW GREEN ARC AT FULL POWER WITH OIL TEMP IN THE MIDDLE OF THE GREEN. IT WAS FOUND THAT OIL PRESSURE GAGE WAS READING 10 PSI LOWER THAN CALIBRATED EXTERNAL GAGE. A NEW KIT WAS INSTALLED WHICH BROUGHT THE ERROR BELOW 6 PSI. THE POPPET VALVE AND SPRING WERE REPLACED, ENGINE RUNS WERE CARRIED OUT AND ACFT RELEASED.