B737 Undifferentiated or Other Model
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 65.35; Flight Crew Total 2307.22; Flight Crew Type 239.72
Situational Awareness; Distraction; Workload
Aircraft Equipment Problem Critical; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Diverted; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Landed in Emergency Condition; Flight Crew Inflight Shutdown
Aircraft; Human Factors
Flight began from ZZZ as second leg of duty day.  Start; taxi and takeoff were uneventful.  Shortly after reaching cruise altitude of FL280; we noticed a low oil qty (0%) and dropping oil pressure (approximately psi). I called for QRH and Captain began running Low Oil Pressure Checklist.  While accomplishing the checklist; the oil pressure dropped below 15 psi and entered the Warning (Red) regime.  This drove us to shutdown the #1 engine.  Captain advised ATC and a gradual descent to FL 250 was initially begun.  After the shutdown was completed; we elected to begin diverting to ZZZ1 as it was only 50 miles away.  ATC; Flight Attendants and dispatch were all provided with necessary information to assist us as we requested Rwy XXL; but due to heavy traffic and closure of XXC; ATC requested we use XXR.  Landing data was run by both crew and dispatch and stopping distance was sufficient on the shorter runway.  While descending; I was momentarily distracted by the runway change and while simultaneously slowing to 200 kts Inattention caused us to slow to approximately 189 kts and we received an 'Airspeed Low' warning.  I accelerated back to 210 kts and requested Flaps 5.  We executed a normal approach and landing with 5 extra kts of speed due to a '10 kts of gain' on final report.  Once we landed; we exited the runway and requested Fire Chief to check us out.  After receiving the all clear; we taxied uneventfully to the gate and accomplished all checklists.  All events were debriefed in accordance with company debrief card.
B737 flight crew reports inflight shutdown and airspeed low warning in descent.