Narrative:

Little over an hour into the flight; I noticed that the oil quantity on the #1 engine was at 16%. All other indications were normal. I began getting in touch with dispatch and [maintenance]; to advise them of the situation. I advised [maintenance] that the engine oil quantity was steadily decreasing; we were losing [about] 1% about every 10 minutes. [Maintenance] advised us that as long as the oil temp. And pressure was in the green; we are good; not worried about oil quantity; just about the oil temperature and oil pressure. [About 40 minutes later]; we had an indication of 0% oil quantity. The oil pressure was normal at 47; and the oil temp. Was normal at 85. All other indications were normal. We continued on to [destination]. Approx. 150 nautical miles out; we started getting erratic fluctuations in the oil pressure from 37 psi to as low as 23 psi. At that point and time first officer (first officer) and I decided we were going to start a slow descent. We [advised ATC] due to 0% oil quantity and the erratic oil pressure. We decided to disconnect the auto throttles after we started descent. I brought the #1 engine to idle. I started the APU for a backup; in case we needed it. I briefed the F/a's (flight attendants) on our situation. I made a PA to the passengers reassuring them that everything was going to be ok; that we had some erratic engine indications and had to get priority to the airport. ATC asked us if we were able to stay on arrival and descend via the arrival; we told them that we were. As we descended; the #1 engine stabilized; the oil pressure stabilized at 26 psi. The oil temperature had increased to 119 from 85. At this point [the first officer] and I decided to keep the #1 engine at idle power until we configured over the marker for a normal configuration of flaps 30 degrees and a 2 engine landing. [The first officer] and I had reviewed the 1 engine approach and landing checklist; and the 1 engine missed approach checklist in case the engine failed. On approach the oil pressure stayed at 31 psi stable. The oil temperature was normal. After landing; [the first officer] and I decided to shut down the #1 engine due to it possibly being oil soaked; to eliminate the possibility of a fire with no air flow over it. After talking with the fire marshal at the gate; they said there was a large puddle of oil under the left engine; after we stopped off the runway. The F/a's did an awesome job in keeping everyone calm. [The first officer's] input and decision making skills made him a major asset to the flight deck.

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Original NASA ASRS Text

Title: B737 NG flight crew reported #1 engine oil quantity gradually decreased to zero enroute to destination.

Narrative: Little over an hour into the flight; I noticed that the oil quantity on the #1 engine was at 16%. All other indications were normal. I began getting in touch with dispatch and [maintenance]; to advise them of the situation. I advised [maintenance] that the engine oil quantity was steadily decreasing; we were losing [about] 1% about every 10 minutes. [Maintenance] advised us that as long as the oil temp. and pressure was in the green; we are good; not worried about oil quantity; just about the oil temperature and oil pressure. [About 40 minutes later]; we had an indication of 0% oil quantity. The oil pressure was normal at 47; and the oil temp. was normal at 85. All other indications were normal. We continued on to [destination]. Approx. 150 nautical miles out; we started getting erratic fluctuations in the oil pressure from 37 psi to as low as 23 psi. At that point and time FO (First Officer) and I decided we were going to start a slow descent. We [advised ATC] due to 0% oil quantity and the erratic oil pressure. We decided to disconnect the auto throttles after we started descent. I brought the #1 engine to idle. I started the APU for a backup; in case we needed it. I briefed the F/A's (Flight Attendants) on our situation. I made a PA to the passengers reassuring them that everything was going to be ok; that we had some erratic engine indications and had to get priority to the airport. ATC asked us if we were able to stay on arrival and descend via the arrival; we told them that we were. As we descended; the #1 engine stabilized; the oil pressure stabilized at 26 psi. The oil temperature had increased to 119 from 85. At this point [the First Officer] and I decided to keep the #1 engine at idle power until we configured over the marker for a normal configuration of flaps 30 degrees and a 2 engine landing. [The First Officer] and I had reviewed the 1 engine approach and landing checklist; and the 1 engine missed approach checklist in case the engine failed. On approach the oil pressure stayed at 31 psi stable. The oil temperature was normal. After landing; [the First Officer] and I decided to shut down the #1 engine due to it possibly being oil soaked; to eliminate the possibility of a fire with no air flow over it. After talking with the Fire Marshal at the gate; they said there was a large puddle of oil under the left engine; after we stopped off the runway. The F/A's did an awesome job in keeping everyone calm. [The First Officer's] input and decision making skills made him a major asset to the flight deck.

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.