What was found
(CAN) ON DESCENT THROUGH APPROX FL120, THE CAPTAIN NOTICED THE NR 1 ENGINE OIL PRESSURE GAUGE WAS INDICATING 0 PSID. THIS INDICATION WAS NOT ACCOMPANIED BY THE MASTER WARNING AND NR 1 ENGINE OIL PRESSURE WARNING LIGHT AND ASSOCIATED AURAL ALERT. WITH CHANGES IN TORQUE THE NR 1 ENGINE OIL PRESSURE GAUGE STARTED TO INDICATE BETWEEN 10 -20 PSID. CONSIDERATION WAS GIVEN TO THE POSSIBILITY OF AN INDICATION PROBLEM DUE TO THE ABSENCE OF THE MASTER WARNING, BUT AFTER A DISCUSSION BETWEEN THE CAPTAIN AND F/O, THE CREW DECIDED TO CARRY OUT THE ENGINE FAIL/FIRE/SHUTDOWN RECALL. THE NR 1 ENGINE WAS SHUTDOWN AT APPROX 7000- 8000 FT. A PAN WAS DECLARED THEN THE ENGINE SHUTDOWN, REF ITEMS WERE COMPLETED. ENGINEERING DESCRIPTION: DEFECT: NR 1 OIL PX GAUGE INDICATED ZERO PSI IN FLIGHT. PX INDICATIONS STARTED TO FLUCTUATE BETWEEN 10-20 PSI WITH POWER CHANGES ENGINE WAS THEN SHUTDOWN. INDICATOR SWAPPED FOR TROUBLESHOOTING, FAULT PRESENT IN NR 1 IND. RETURNED TO ORIGINAL SIDES. NR 1 OIL PRESSURE TRANSMITTER REPLACED LEAK CHECK C/O SERV TEST C/O SERV IAW MM 79-36-01.