CREW HAD EICAS WARNING OF LOW OIL PRESSURE.

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THE FO WAS FLYING THE DEP FROM RWY 2L AT BNA. JUST PRIOR TO THE 1000 FT CALL WE RECEIVED A MASTER WARNING TRIPLE CHIME AND AN AURAL 'OIL PRESSURE' ALONG WITH A 'R ENG OIL PRESSURE' MESSAGE ON THE EICAS. CHKING THE OIL PRESSURE GAUGE; WE FOUND OIL PRESSURE WAS FLUCTUATING BUT WITHIN GREEN PRESSURE READOUTS. A DECISION WAS MADE TO RETURN TO LNDG; CONTINUING AROUND THE PATTERN WITH THE ENG OPERATING AND MONITORING ITS OIL PRESSURE. DURING THE BRIEF PATTERN; THE R ENG OIL PRESSURE WAS CONTINUING TO FLUCTUATE BTWN 25 PSI AND WELL OVER 40 PSI AND ALL OTHER ENG PARAMETERS; INCLUDING OIL TEMP WERE READING NORMAL. NO EMER WAS DECLARED AND THE CTL TWR WAS VERY HELPFUL IN CLRING US TO LAND FROM A DOWNWIND POS ON RWY 2L. THE APCH AND LNDG WERE UNEVENTFUL AND THE R ENG WAS SHUT DOWN DURING THE TAXI TO THE GATE. THE FLT ATTENDANT WAS ADVISED IN FLT OF THE RETURN TO LNDG AND WHY. THE FLT ATTENDANT ADVISED THE PAX OF THE RETURN. CONTRACT MAINT ARRIVED TO ASSESS THE PROB. R ENG OIL WAS SVCED (LESS THAN 1/2 QUART) AND THE CHIP DETECTOR WAS CHKED AND FOUND CLEAN. NO OTHER ANOMALIES WERE FOUND. THE ENG WAS GND RUN WITH ALL INDICATIONS NORMAL AND THE ACFT WAS SIGNED OFF TO BE FERRIED TO CVG.