What was found
(CAN) DURING CRUISE, THE PILOT NOTICED THE ENGINE OIL PRESSURE BEGINNING TO FLUCTUATE BETWEEN 55-65 PSI AND DROPPING DOWN TO LOWER THAN 55 PSI. PILOT ELECTED TO RETARD THE PLA TO FLIGHT IDLE TO LOWER THE NH SPEED BELOW 75 PERCENT. WITH THE PLA AT FLIGHT IDLE, NH WOULD NOT DROP BELOW 75 PERCENT, SO PILOT ELECTED TO FEATHER THE PROPELLER. ABOUT 30 SECONDS LATER, THE PILOT STARTED TO SEE THE ITT INCREASING AND ELECTED TO SHUTDOWN THE ENGINE. AN UNEVENTFUL SINGLE ENGINE LANDING WAS MADE.