What was found
WHILE EN ROUTE AT 16,000 FT, NOTICED THE LEFT PROP OIL PRESSURE INDICATING 160 PSI, COMPLETED QRH. MONITORED PROP OIL PRESSURE WAS FLUCTUATING UP TO 190 PSI. DIVERTED TO MKG. MAINTENANCE INSPECTED LT PGB OIL SYSTEM, RAN A/C AT HIGH POWER SETTING TO DUPLICATE PROBLEM, INSTALLED NEW RT GAUGE. ALL CHECKS NORMAL.