What was found
DEPARTED DENVER. EVERY INDIRECTION ON TAKEOFF & CLIMB WAS NORMAL UNTIL 10 MINUTES INTO CRUISE AT 16,000FT, WHEN TORQUE GAUGE BECAME ERRATIC, PILOT WATCHED GAUGE FOR ABOUT A MINUTE & TAPPED GAUGE A FEW TIMES TO CHECK IF IT WAS GETTING STUCK. THE LOW OIL PRESSURE LIGHT CAME ON FOR LT ENGINE. PRESSURE ON ENGINE WAS 50PSI. DECIDED TO RETURN TO DIA , ADVICED ATC NEEDED TO RETURN BUT DID NOT DECLARE AN EMERGENCY. LANDED WITHOUT INCIDENT. ENTIRE WAY BACK, THE ENGINE CONTINUED TO LOSE OIL PRESSURE DOWN TO BELOW REDLINE ENGINE WAS OPERATING NORMALLY & FELT PERFECTLY NORMAL WITH NO INDICATIONS THAT WOULD SUGGEST A FAILURE. ELECTED TO KEEP THE ENGINE RUN. ONCE SAFELY ON THE GROUND, SHUTDOWN ENG AND TAXIED TO RAMP.