CRJ 200 Captain reported fluctuating oil pressure on the left engine caused an in flight shut down. The flight crew ran the appropriate checklists and continued to the destination airport.

Narrative

Operating Aircraft X ZZZ to ZZZ1; after taxiing the aircraft from the ramp area to Runway XXL; the flight was given taxi instructions for Taxiway 1; Taxiway 2; and Taxiway 3. After starting the taxi on Taxiway 1 the Captain started to follow the wrong line leading to Taxiway 4; but immediately made corrections before encroaching Taxiway 4 and made a normal ground operations turn and continued to taxi without incident. The flight was cleared for takeoff and began the climb out without incident. Once reaching 10;000 feet; the flight began accelerating and was given normal speed. During the climb the Captain noticed the Left engine oil pressure fluctuating between 25-53 PSI at the lowest and highest peaks. In general it was on average between 53-40 PSI. A maintenance message was sent to Dispatch about this issue and the reply was only if the warning messages were displayed and that they copied the receipt of the ACARS message. Then crew reviewed the engine low oil pressure QRH (Quick Reference Handbook) and reviewed the aircraft logbook history in detail and discovered that the aircraft had a history of fluctuating oil pressure and that it was placed on an oil watch. Maintenance had made multiple log entries describing that anywhere between 1 to 1.5 pints had been added over the course of about a month. Then about 2 weeks before the flight in question the left engine was removed from oil watch and signed off. After checking the history the flight crew thought; since the problem was signed off; that there was a possibility that it was a faulty gauge considering there was no other abnormal indications. The flight continued without incident and was being vectored to intercept the final approach course at the final approach fix. I believe the first time we got the intermittent left oil pressure warning was about 800 feet AGL. Both crew members elected to continue; the message did come on a second time then extinguished. The 500 foot stabilized call was made then the warning message came on again. The decision was made to shutdown the left engine before it failed on its own and a request for priority handling was made. Aircraft landed safely and taxied to the gate. Both crew members were completely unaware of the engine oil fluctuation QRH procedure that was in the back of the power plant section of the QRH. I feel if the engine oil QRH procedures were grouped together or at least referenced each other this incident could have been avoided.