ATR-72 First Officer reported a warning chime during takeoff roll that was evaluated after takeoff indicating fluctuating oil pressure. Later in flight oil pressure fluctuations went into yellow range so crew performed precautionary shutdown and diverted in for a single engine landing. Crew observed flat tires on left side after entering ramp area causing airplane to list to that side during parking.

Narrative

CA (Captain) was flying pilot. Received transient chime during takeoff at v1/vr with no residual caption; procedure; alert; local alert or open status item. Runway heading to 3;000 ft. On climb out after takeoff checklist; a check of system pages revealed left engine oil pressure fluctuating up and down. Kept engine parameters system page open to monitor. Captain advised of situation. Upon reaching cruising altitude of 15;000 feet engine oil pressure fluctuating green to yellow and back again. Assessed situation; contacted dispatch via phone patch to ARINC; decided to execute precautionary engine shutdown; accomplish checklist items; discuss status; [request priority handling] and request direct to ZZZ. Dispatch amendment received diverted to ZZZ. Flight attendant briefed; and passengers informed of diversion to ZZZ. Captain executed a single engine approach to landing ILS Runway XXL ZZZ approach to land and landed on centerline and well within landing threshold. Easy on brakes and vacated runway at the last exit. Waited for escort follow along before taxi to ramp. When entering ramp area noticed flat tires left side as the airplane listed onto flat tires on turn to park.