What was found
(CAN) DURING CRUISE, CREW NOTICED OIL PRESSURE DROPPING, PRIOR TO LOWER LIMIT, ENGINE WAS SECURED/SHUTDOWN. FLIGHT CONTINUED TO DESTINATION 20 MINUTES OUT AND LANDING COMPLETED WITHOUT INCIDENT. ENGINE STRIP INDICATES ANOTHER (BLACK OIL/CARBON IN OIL) ENGINE AS ROOT CAUSE FOR LARGE AMOUNTS OF CARBON CONTAMINATING BEARINGS AND PASSAGES. NUMBER TWO BEARING RUNNING DRY AND NUMBER 3 BEARING RUNNING DRY AND FAILED. (ENGINE IS PRE SB14325.) ENGINE WAS REPLACED AND THE AIRCRAFT RETURNED TO SERVICE.