What was found
(CAN) THE ACFT WAS PARKED FOR THE PAST 4 YEARS AND CLAIMED TO HAVE HAD MONTHLY GROUND RUNS PERFORMED TO PREVENT LONG TERM STORAGE/PRESERVATION. THE OIL LEVEL WAS CHECKED GOOD ON THE 2 ENGINES ON OCTOBER 21ST JUST BEFORE A REPOSITIONING FLIGHT AS THE CUSTOMER INTENDED TO LEASE THE ACFT. THE ACFT HAD TO RETURN TO DEPARTURE AIRPORT DUE TO A LOW OIL PRESSURE WARNING. 1 OF THE 2 ENGINES APPARENTLY HAD AN OIL PRESSURE LIGHT COME ON DURING FLIGHT. THE SISTER ENGINE REPORTED TO HAVE HAD IT`S OIL PRESSURE DROP TO 20 PSI AFTER THE ACFT GOT ON GROUND. OIL WAS SEEN COMING OUT OF THE BREATHER LINE ON THE 2 ENGINES.