B767-300 First Officer reported that shortly after reaching cruise altitude; a decrease in #1 engine oil quantity was observed; followed by fluctuating oil pressure indications. A successful diversion was accomplished; and the engine remained operational until landing.

Narrative

After takeoff and climb out in ZZZ the Relief Pilot set up the rest breaks. Once our first crew swap occurred we were about 45 minutes prior to oceanic. During our crew change we notice a lower oil quantity than normal but well within a normal operating range. We continued to monitor it and as the oil quantity dipped even further we woke up the CA from his break to discuss our options. The FOs had reached out to Maintenance Control twice via ACARS with no response; then via dispatch after a delay then received a response. Once the CA had arrived the crew completed a SATCOM call with dispatch and Maintenance Control the crews decision was to turn around. Dispatch asked that if the engine was working normal with a 0 oil quantity to fly to ZZZ1 as long as everything was working. We continued a constant analysis of airports between us and ZZZ1 to assess scenarios if the situation degraded. The oil pressure remained stable then about 40-30 minutes outside of ZZZ2 the oil pressure began to fluctuate. The crew decided to divert to ZZZ2; dispatch was notified and priority handling was then requested. An uneventful landing was conducted into ZZZ2. On taxi in the ENGINE. 1 was shut down; but had continued to work within parameters for the duration of the flight.