Narrative:

Approximately 3 hours into the flight; oil quantity in the left engine decreased 3 quarts. After discussing it; we decided to initiate a diversion and try to return to ZZZ. We were unable to obtain a clearance from ZZZ center while at FL370 and on our assigned track; therefore; following flight manual guidance; we declared an emergency; offset 15 NM north of track and descended to FL310 so that we could obtain such clearance. Our initial intent was to try to fly to ZZZ since oil quantity was holding steady at 3 quarts and all other engine indications were normal. Contacted dispatch and established a 3 way phone patch with maintenance control who agreed that our situation most likely was an oil quantity issue instead of just a bad indication since the fuel oil heat exchanger had been replaced just prior to this ETOPS flight. As we progressed wbound towards ZZZ; oil quantity eventually dropped to zero and oil pressure started to drop and fluctuate. It became obvious that ZZZ was no longer a viable option since oil pressure would soon be below limits. The simple decision to make was; where to shut the engine down when the associated irregular procedure directed it. The answer was simple; after landing; instead of in flight. We decided to divert into ZZZZ. The engine continued to operate normally with all indications except oil quantity remaining within limits. The low oil pressure EICAS warning came on at touchdown. The engine was shutdown during taxi-in. Followed flight manual guidance. Dispatch and maintenance control were notified and were involved during the entire diversion. A cabin advisory was issued.

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Original NASA ASRS Text

Title: A B777 LOST OIL QTY ON AN OCEANIC TRACK AND DIVERTED TO A NEARBY ARPT. AN EMER WAS DECLARE BUT THE ENG REMAINED RUNNING UNTIL LNDG.

Narrative: APPROX 3 HRS INTO THE FLT; OIL QUANTITY IN THE L ENG DECREASED 3 QUARTS. AFTER DISCUSSING IT; WE DECIDED TO INITIATE A DIVERSION AND TRY TO RETURN TO ZZZ. WE WERE UNABLE TO OBTAIN A CLRNC FROM ZZZ CTR WHILE AT FL370 AND ON OUR ASSIGNED TRACK; THEREFORE; FOLLOWING FLT MANUAL GUIDANCE; WE DECLARED AN EMER; OFFSET 15 NM N OF TRACK AND DSNDED TO FL310 SO THAT WE COULD OBTAIN SUCH CLRNC. OUR INITIAL INTENT WAS TO TRY TO FLY TO ZZZ SINCE OIL QUANTITY WAS HOLDING STEADY AT 3 QUARTS AND ALL OTHER ENG INDICATIONS WERE NORMAL. CONTACTED DISPATCH AND ESTABLISHED A 3 WAY PHONE PATCH WITH MAINT CTL WHO AGREED THAT OUR SITUATION MOST LIKELY WAS AN OIL QUANTITY ISSUE INSTEAD OF JUST A BAD INDICATION SINCE THE FUEL OIL HEAT EXCHANGER HAD BEEN REPLACED JUST PRIOR TO THIS ETOPS FLT. AS WE PROGRESSED WBOUND TOWARDS ZZZ; OIL QUANTITY EVENTUALLY DROPPED TO ZERO AND OIL PRESSURE STARTED TO DROP AND FLUCTUATE. IT BECAME OBVIOUS THAT ZZZ WAS NO LONGER A VIABLE OPTION SINCE OIL PRESSURE WOULD SOON BE BELOW LIMITS. THE SIMPLE DECISION TO MAKE WAS; WHERE TO SHUT THE ENG DOWN WHEN THE ASSOCIATED IRREGULAR PROC DIRECTED IT. THE ANSWER WAS SIMPLE; AFTER LNDG; INSTEAD OF IN FLT. WE DECIDED TO DIVERT INTO ZZZZ. THE ENG CONTINUED TO OPERATE NORMALLY WITH ALL INDICATIONS EXCEPT OIL QUANTITY REMAINING WITHIN LIMITS. THE LOW OIL PRESSURE EICAS WARNING CAME ON AT TOUCHDOWN. THE ENG WAS SHUTDOWN DURING TAXI-IN. FOLLOWED FLT MANUAL GUIDANCE. DISPATCH AND MAINT CTL WERE NOTIFIED AND WERE INVOLVED DURING THE ENTIRE DIVERSION. A CABIN ADVISORY WAS ISSUED.

Data retrieved from NASA's ASRS site as of May 2009 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.