Narrative:

In cruise at FL290 approaching ZZZZ1; the first officer and I noticed the left engine oil quantity at 1 quart and the left engine oil pressure slowly dropping; while the right engine remained stable. We called dispatch immediately and had a phone patch to [maintenance control] to discuss the issue. The oil pressure continued to drop during our roughly 3 minute discussion. Based on our current position; we all agreed the safest and most prudent course of action was to divert back to ZZZZ. The first officer immediately called for the 2 relief officers; who were currently on break; to return to the cockpit. Everyone was briefed on the situation; as we had already turned back to ZZZZ. We informed the purser of the issue and asked they begin picking up all trays and secure the cabin for landing in approximately 55 minutes. We also informed the passengers of our return to ZZZZ because of the situation. As we continued toward ZZZZ; the oil pressure continued to drop. We then [advised ATC] with ZZZZ1 ATC as it was becoming apparent we would eventually be shutting down the left engine; wanting priority handling to ZZZZ. We also began dumping fuel; which took 31 minutes to complete; to get us below an overweight landing situation. When the right engine pressure dropped to 14; we elected to disarm the left auto throttle and bring it to idle. We descended to FL240. Within 3 minutes of descending; the oil pressure was reading 9; the oil quantity was 0; [using] the ecl [electronic checklist] [for] the engine shutdown checklist. We shut the left engine down as per the checklist. The purser was notified of the current situation (test) and prepared the cabin as necessary. We asked ZZZZ center to coordinate fire trucks at the airport for our return. We briefed an ILS to [runway] 16R single engine auto land approach. We landed in ZZZZ without incident; taxied to a hardstand gate and deplaned passengers to buses. The ZZZZ aviation authority came on board the aircraft; asked us to write an incident report and took photos of our licenses and medicals before releasing us to leave the aircraft. I spoke directly with the [maintenance control] and dispatch just prior to ZZZZ authorities boarding the aircraft; recapping the entire incident. [We] debriefed with our local mechanics of the engine issue and parameters we encountered prior to shutting down the left engine before leaving the aircraft and returning to the hotel. The incident began 53 minutes into the flight. We were back in ZZZZ in less than 1 hour after the incident began.

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Original NASA ASRS Text

Title: B777 flight crew observed low oil quantity and shutdown engine and returned to departure airport.

Narrative: In cruise at FL290 approaching ZZZZ1; the First Officer and I noticed the left engine oil quantity at 1 quart and the left engine oil pressure slowly dropping; while the right engine remained stable. We called dispatch immediately and had a phone patch to [Maintenance Control] to discuss the issue. The oil pressure continued to drop during our roughly 3 minute discussion. Based on our current position; we all agreed the safest and most prudent course of action was to divert back to ZZZZ. The First Officer immediately called for the 2 Relief Officers; who were currently on break; to return to the cockpit. Everyone was briefed on the situation; as we had already turned back to ZZZZ. We informed the Purser of the issue and asked they begin picking up all trays and secure the cabin for landing in approximately 55 minutes. We also informed the passengers of our return to ZZZZ because of the situation. As we continued toward ZZZZ; the oil pressure continued to drop. We then [advised ATC] with ZZZZ1 ATC as it was becoming apparent we would eventually be shutting down the left engine; wanting priority handling to ZZZZ. We also began dumping fuel; which took 31 minutes to complete; to get us below an overweight landing situation. When the right engine pressure dropped to 14; we elected to disarm the left auto throttle and bring it to idle. We descended to FL240. Within 3 minutes of descending; the oil pressure was reading 9; the oil quantity was 0; [using] the ECL [Electronic Checklist] [for] the Engine Shutdown Checklist. We shut the left engine down as per the checklist. The Purser was notified of the current situation (TEST) and prepared the cabin as necessary. We asked ZZZZ Center to coordinate fire trucks at the airport for our return. We briefed an ILS to [Runway] 16R single engine auto land approach. We landed in ZZZZ without incident; taxied to a hardstand gate and deplaned passengers to buses. The ZZZZ Aviation Authority came on board the aircraft; asked us to write an incident report and took photos of our licenses and medicals before releasing us to leave the aircraft. I spoke directly with the [Maintenance Control] and Dispatch just prior to ZZZZ authorities boarding the aircraft; recapping the entire incident. [We] debriefed with our local mechanics of the engine issue and parameters we encountered prior to shutting down the left engine before leaving the aircraft and returning to the hotel. The incident began 53 minutes into the flight. We were back in ZZZZ in less than 1 hour after the incident began.

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.