Workload; Troubleshooting; Situational Awareness
Aircraft Equipment Problem Critical
Flight Crew Diverted; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action; General Maintenance Action
Aircraft
We were at cruise when our oil pressure started to indicate low in the amber range (Captain detected).  We ran the QRH at this time and it did not require an engine shutdown.  Within minutes the oil pressure dropped and remained in the red.  The QRH called for a precautionary shutdown.  We had already called center and requested to divert as a precautionary.  At this time the Captain (CA) turned toward the airport with the help of ATC.  We were becoming pretty task saturated and were preparing to shut down the number 1 engine and the CA made the comment that we needed to slow down.  We did. We shut down number one; ran checklists and prepared for the divert including getting the speeds for a flaps 22 single engine approach; briefed the possible go-around as it was overcast and gusty. The CA notified the Flight Attendant (FA) and also the jumpseating FA who had also stepped up to assist.  ATC gave us several turns to assist in the descent and we intercepted the LOC for RWY XY at 7000 ft.; completed the single engine approach and taxied to the ramp.  While conducting a walk around; we found the nacelle (lower portion) covered in oil as well as the area behind the engine.  There were many threats; however I feel that given the situation they were all managed very; very well.  It was a positive outcome. It appears that this was a maintenance issue so I do not believe that we could have prevented the issue.   One thing I cannot emphasis enough is that the company should NEVER ask a pilot to fly immediately after an event of this nature. I don't know that they are aware of the physiological effects that happen to a pilot after something like this and they are things that actually take time to develop.
Seconds later I noticed an irregularity with the ENG1 Oil pressure.  It had sporadically dropped from about 60 to 40ish and back up.  I saw it happen a few times within seconds so I requested the First Officer (FO) to QRH Low oil pressure.  I simultaneously pulled up the takeoff data page and observed the oil quantity at 3 quarts.  The FO ran the QRH and at that point still had oil pressure within limits so we elected to divert while the engine was still good.  I sent a [message] to dispatch that we were diverting due to low oil; and informed the FA that we were diverting for precautionary reasons and informed the pax.  Within about two minutes the situation escalated to where the QRH directed a shutdown.  The low oil quantity also advised the same.
An EMB-145 engine oil pressure initially dropped; stabilized; then dropped into the RED band. The QRH was referenced; the engine shutdown; and the flight diverted to a nearby airport.