Date: 202103
Local time of day: 1801-2400
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737 MAX 8
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise; Descent
ATC / advisory: Center ZZZ
Aircraft component: Oil Indicating System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Commercial; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human factors: Human-Machine Interface; Troubleshooting; Situational Awareness
Anomaly: Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Aircraft
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Clearance; Flight Crew Overcame Equipment Problem; General Maintenance Action
Contributing factors: Aircraft; Equipment / Tooling
Primary problem: Aircraft

Narrative: About XX minutes after we reached our cruise altitude; my FO (First Officer) and I observed the level on our #2 Oil Qty gauge go from 11 to Y then Z; then blank rather quickly.  It had been normal up until then; we just caught the decrease at 11. After checking the QRC and QRH for Low Oil Qty to no avail; we noticed our #2 Oil Pressure dropping. It stabilized at 29 psi but fluctuated from XX to XY with 29 being the median amber band.  This continued for the remainder of the flight until TOD (Top of Descent).  I referenced the Engine Low Oil Pressure Checklist in the QRH on Page X.XX.  It states that if the oil pressure is at or below the redline: Go to the Engine Failure or Shutdown checklist on Page X.XY. The oil pressure never reached the redline; so the checklist stops there.  All other engine parameters were normal with no vibration.  My FO (First Officer) continued to fly and talk with ATC while I set up a phone patch with our Dispatcher as I decided that there was too much information to use ACARS.  I told them what was going on and that we were continuing on to ZZZ but we were also prepared to divert if need be later on.  They were in agreement as there was no need or requirement at this time to shut the engine down or divert.  I talked with the Flight Attendants and we had a good discussion about the situation.  I told them that our aircraft was operating just fine and that it seems that we have an indication issue and that I was not going to make a PA.  I also asked them if they could discretely look at the aft portion of the right hand engine to see if they saw any oil.  My FO (First Officer) and Flight Attendants did a great job along with our Dispatcher and Maintenance Control.  Later in the flight; our Dispatcher gave us single engine landing data for ZZZ.  Descending into ZZZ when the thrust levers were slowly retarded to idle; the oil pressure and qty actually increased.  By the time we were on final approach; the said indications were normal.




Synopsis: B737 MAX 8 Captain reported shortly after arriving at cruise altitude the number 2 Engine oil quantity indication rapidly decreased and extinguished. During approach all indications returned to normal.