B737 flight crew reported a diversion due to engine oil quantity decreasing in flight.

Attributes
ACN	1452426
Time
Date	201705
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	B737 Next Generation Undifferentiated
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Powerplant Lubrication System
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 272
Person 2
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 316
Events
Anomaly	Aircraft Equipment Problem Less Severe

Narrative:

Upon receipt of the aircraft; the logbook indicated a previous day write-up for 'excessive oil consumption' on engine number 1. The signoff read; 'replaced magnetic seal; no leaks noted.' oil levels were: number 1: 88 percent; number 2: 100 percent. 1.75 hours into the flight; the number 1 was at 49 percent. I notified dispatch and we continued to monitor the oil loss. Later; 37 percent; and then later 28 percent. At one time I asked dispatch if they had a preference of action. He said that they had been looking at this long enough. They were ready for either. Operationally; it would be best to continue on [to ZZZ]; maintenance wise; it would be best to land in ZZZ1. We were estimating landing at ZZZ with 10-15 percent oil quantity. Not knowing at what point we might begin to experience temperature and pressure issues; combined with the possibility of landing single engine at a special airport with a 3.5 degree GS; the first officer; dispatcher; and I agreed that a divert to ZZZ1 was the most prudent decision. Landing was uneventful. Upon arriving at the gate; maintenance was about 99 percent sure what the problem was and thanked us for 'not toasting the engine!'

Original NASA ASRS Text

Title: B737 flight crew reported a diversion due to engine oil quantity decreasing in flight.

Narrative: Upon receipt of the aircraft; the logbook indicated a previous day write-up for 'Excessive oil consumption' on engine number 1. The signoff read; 'Replaced magnetic seal; no leaks noted.' Oil levels were: number 1: 88 percent; number 2: 100 percent. 1.75 hours into the flight; the number 1 was at 49 percent. I notified Dispatch and we continued to monitor the oil loss. Later; 37 percent; and then later 28 percent. At one time I asked Dispatch if they had a preference of action. He said that they had been looking at this long enough. They were ready for either. Operationally; it would be best to continue on [to ZZZ]; Maintenance wise; it would be best to land in ZZZ1. We were estimating landing at ZZZ with 10-15 percent oil quantity. Not knowing at what point we might begin to experience temperature and pressure issues; combined with the possibility of landing single engine at a special airport with a 3.5 degree GS; the First Officer; Dispatcher; and I agreed that a divert to ZZZ1 was the most prudent decision. Landing was uneventful. Upon arriving at the gate; Maintenance was about 99 percent sure what the problem was and thanked us for 'not toasting the engine!'

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.