B737-800
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Total 20500
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Diverted; Flight Crew Inflight Shutdown
Aircraft
In cruise at FL380; we were deviating around thunderstorms running north-south along the front range of the mountain ranges. While navigating through a gap south of ZZZ toward [a fix]; we noticed the engine oil quantity in the left engine had gone to zero and displayed reverse video. Shortly after that; the engine oil pressure became erratic. We followed the QRH procedures for low oil quantity followed by the QRH for low engine oil pressure. These checklists lead us to the Precautionary Engine Shut Down Checklist. We descended to FL220 and completed the Precautionary Shut Down Checklist. I notified ATC. I called dispatch and informed them of our situation. Due to weather and terrain considerations; we decided ZZZ1 was the safest [and] most suitable airport. I talked to the flight attendants and informed them of our situation following the guidance of our Non-routine Landing Checklist in the QRH. I informed them we planned a routine approach and landing and had no reason to believe we would need to evacuate. We completed the One Engine Approach and Landing Checklist as well as the Non-routine Landing Guidance in the QRH. We completed the Normal Descent and Before Landing Checklist; briefed and flew the ILS XX at ZZZ1 to an uneventful landing with fire trucks standing by. We came to a complete stop on the runway and I had the fireman visually inspect the aircraft. When given the all clear from ARFF; we taxied to the gate. The event occurred because we lost all of our oil from the left engine.
B737 Captain reported a loss of engine oil quantity and erratic oil pressure led to an in-flight shutdown and diversion.