LOSS OF OIL PRESSURE DUE TO A LEAK RESULTS IN A DIVERSION TO A NEARBY ARPT FOR B757-200.

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ENRTE TO SLC WHILE CRUISING AT FL360; THE CAPT AND I NOTICED A FLICKERING 'R ENG OIL PRESS' CAUTION LIGHT. OIL PRESSURE ON THE INDICATOR WAS IN NORMAL RANGE; BUT FLUCTUATING. THE OIL QUANTITY INDICATOR WAS INDICATING ALTERNATELY BTWN A 'ZERO' AND AN OPEN BOX. OIL PRESSURE ON EICAS BEGAN TO DECREASE. THE CAPT TURNED ATC OVER TO ME AFTER READING THE 'OIL PRESS' CHKLIST AND INITIATED A CALL TO MAINT CTL. MAINT ADVISED US TO RUN THE #2 ENG AT IDLE. WE DISCONNECTED THE AUTOTHROTTLES AND REDUCED THE #2 ENG THRUST TO IDLE. OIL PRESSURE STABILIZED BTWN 90-95 BUT WAS STILL FLUCTUATING. I ASKED ATC FOR A LOWER ALT. MAINT ASKED THE CAPT IF WE COULD MAKE IT TO ZZZ1 OR ZZZ2. AFTER CHKING WX; THE CAPT DECIDED TO DIVERT INTO ZZZ; WHICH WAS CLOSE; AND HAD A MAINT FACILITY; AND WAS RPTING WX OF 9 SM; 6000 FT BROKEN; AND 8000 FT OVCST. ZZZ3 WX WAS 1 1/2 MI AND SNOW. AN EMER WAS NOT DECLARED BECAUSE THE ENG WAS BOTH RUNNING AND STABILIZED. AFTER CONDUCTING THE ILS VIA RADAR VECTORS INTO ZZZ; WE TAXIED CLR OF THE ACTIVE RWY; SHUT DOWN THE #2 ENG AND TAXIED ON OUR L ENG TO GATE WHERE WE WERE MET BY THE FIRE DEPT TO INSPECT OUR ENG. POSTFLT EXAM FOUND OIL LEAKING FROM R ENG.