AN OIL LEAK CAUSED AN ENG SHUTDOWN.

Narrative

THE SECOND ROUNDTRIP OF OUR 3 DAY TRIP WAS FROM STL TO JLN. PREFLT INDICATED BY THE FO; WAS ALL NORMAL INCLUDING THE OIL LEVEL ON BOTH ENGS. WE ARRIVED IN JLN AND DURING OUR GND TIME WE PROCEEDED TO DO A WALK AROUND OF THE ACFT. THE FUELER HAD NOTICED A SMALL BLOTCH OF OIL ON THE RAMP UNDER THE R ENG. I DID NOT THINK THINGS WERE AS BAD AS INDICATED BY SOMEONE WHO WAS NOT A MECH OR PLT. THE ACFT DOES ON OCCASION SPIT OUT FLUIDS THROUGH THE OVERFLOW (GANG DRAIN) IF OVER SERVICED BY MAINT. THE OIL LEVEL WAS CHKED BY THE FO AND MYSELF AND WAS FOUND TO BE THE SAME AS WAS NOTED ON INITIAL PREFLT. WE HAD NO REASON TO BELIEVE THE SMALL BLOTCH OF OIL WAS OF ANY MAJOR CONCERN. WE DETERMINED THE ACFT WAS AIRWORTHY. ABOUT 40 MINS INTO THE FLT; WE HAD A MASTER WARNING 'OIL PRESSURE' ON THE R ENG. WITHIN ABOUT 1 MIN IT CONTINUED TO DROP TO 20 PSI AND BELOW. WE SHUT DOWN THE ENG IN ACCORDANCE WITH THE EMER CHKLIST (EMBRAER). WE ASKED STL APCH FOR PRIORITY HANDLING INTO STL AND LANDED. WE HAD NO REVERSE WITH 1 ENG (YAW) SO WE USED BRAKING TO SLOW US AND EITHER HAD A HOT BRAKE ON THE R SIDE AND BLEW THE R INBOUND TIME ON THE ANTI-SKID HIT A DRY SPOT ON THE RWY SINCE THERE HAD BEEN RAIN THERE EARLIER AND THE RWY WAS A LITTLE DAMP. WE TAXIED IN AND EVERYONE ABOARD WAS FINE. MAINT FOUND A CHAFED OIL LINE WHICH HAD BLOWN ENRTE CAUSING THE OIL TO SPEW OUT SUDDENLY. I WOULD RECOMMEND BETTER PREVENTIVE MAINT PROCS ON-LINE AND IN THE HANGAR. ALSO CLEANING THE ACFT BETTER; AS WELL AS ASSURING THE CLEANING FLUIDS ARE REMOVED SO 'FALSE CONCERNS' WILL NOT OCCUR.