B767 Captain reported observing a decreasing oil quantity during an ETOPS flight in oceanic airspace. The flight diverted to an alternate airport and landed.

Narrative

I was assigned as the Captain on this fight and was the pilot flying. At approximately XA:25 and 2 hours of elapsed flight time I was preparing for my FAA mandated inflight rest period and the oceanic portion of the flight. As is my custom I noted on my personal copy of the flight plan current engine indications. It was at this time that I noticed the number one engine quantity was 6 quarts. To the best of my recollection it was 22 quarts at the gate prior to engine start; well above the minimum 15 quarts. At XA:27 I recorded the following parameters for the left and right engine respectively. Oil Pressure 225/201; Oil Temperature 99/105; Oil Quantity 6/15; VIB 1.4/1.0. While it is normal for this Pratt & Whitney engine to show a large decrease in oil quantity after engine start and while running; this was atypically low. I discussed the situation with the two First Officers and told them to call me if the situation deteriorated. I left the cockpit and began my in flight break.During my break I remained awake and reviewed applicable sections of the Flight Manual as well as reviewed possible diversion airports that were not already listed on the flight plan. Approximately 45 minutes into my break I was notified by the Purser that the FO's (First Officers) would like me to return to the cockpit. When I returned the left engine oil quantity was at 2 quarts and had been losing a quart about every 15 minutes as documented by the relief pilot. I returned to my duty station and they briefed me about items relevant to position; fuel status; communications; etc. We were in oceanic airspace and all appropriate procedures for oceanic entry had been completed. We had an ADS-C connection with ZZZZ Oceanic and a good SELCAL check with ZZZZ Radio. We then began discussing the oil quantity issue with the obvious first question to continue or turn back towards our initial ETOPS alternate. I knew from experience and FM review that Oil Pressure was the controlling parameter and not Oil Quantity. That said we all seemed to be appropriately concerned about the steady decrease in quantity over a relatively short timeframe. I divided duties within the cockpit transferring control and routine comms to the PM and ask the relief pilot to begin checking / verifying our ETOPS alternate was still viable (it was) as well as a potential nearest suitable if it became necessary. We continued in accordance with our clearance as I initiated a SAT call with Dispatch and Maintenance Control and gave them the pertinent information about our situation. The initial part of the discussion with Maintenance Control revolved around the other engine parameters and a check of relevant history on this aircraft. I had previously flown the aircraft days before and knew that this was a new engine with under 100 hours on it. I verified with Maintenance Control that oil pressure was the controlling parameter and while unlikely this could be an indication problem. The Maintenance Control controller did admit that 2 quarts of oil was a concerning indication. I paused the call and relayed the information from Maintenance Control to my crew and at that point I think we were all in agreement that while the engine was running normally and would likely continue to run for some undetermined amount of time even if the oil quantity went to zero; that a precautionary turn back was the correct decision given the information that we had at the time. It was at this time that I requested via CPDLC a revised clearance back to our oceanic entry point with an alternate airport to be communicated soon. This decision felt time critical in the moment since we were filed under 180 minute ETOPS rules and our CP (Critical Point) was rapidly approaching even though we had not been in oceanic airspace for very long. In hindsight and remembering that the fuel delta at the CP was almost 20.0 LBS it seems less critical now other than the obvious fact that the nearest land mass was behind us and we had already decided to turn back. This decision led to some communication issues that I will detail fully below. Suffice it to say that it is not possible in this aircraft type to conduct a SAT call and communicate over HF with ATC / radio operator simultaneously.The discussion next turned to the Dispatcher and what was available as an alternate. The Dispatcher floated the idea of diverting to ZZZ for passenger accommodation and possible repairs with the obvious condition that the left engine continued to run normally at full rated thrust and no other signs of degradation. It seemed like a reasonable request and we discussed it as a crew. Our immediate concern was not only the weather conditions and the distance to ZZZ but having several available alternates along the way in case the situation deteriorated. The weather was challenging with various combinations of strong winds; low ceilings and visibility; and various runway and airport conditions related to freezing precipitation. After what seemed like an extensive discussion with Dispatch and crew we decided on a 'stepping stone' approach of suitable alternates along the way to ZZZ. I made the decision to name ZZZ as the new destination and communicated that to ATC. It should be noted that at this time the engine was running and performing normally.After coordinating with ATC; the Flight Attendants; and the passengers; we settled in for the long divert to ZZZ. We continued to discuss weather and monitor our list of alternates. We reviewed the FOM diversion guide which we had used as a guide earlier but wanted to make sure we had covered all the big picture items. We also discussed how to evaluate the engine performance as we continued and focused on the oil pressure and temperature as the oil quantity was now reading zero. The engine continued to run normally.After approximately 3 hours and with about 1 hour remaining to ZZZ in the vicinity in ZZZ1 the relief pilot brought to our attention that the oil pressure on the left engine had begun to fluctuate slightly. It had been running steadily and approximately matched with the right engine but now it was fluctuating between about 165-170 PSI. More concerning was a discernible downward trend. When the pressure fluctuation reached 140 PSI we had a short discussion as a crew and decided while the pressure was still more than twice the minimum of 70 PSI it was probably wise to divert to ZZZ1 which was just left of the nose for approximately 80NM. We communicated our intentions and updated situation to ATC and requested priority handling as a precaution to give us flexibility to deal with any sudden change in circumstances.Somewhere during the divert I resumed PF duties and I briefed a two engine visual approach to Runway XXL at ZZZ1 with an ILS backup. ZZZ1 was VMC but had a quartering headwind gusting to nearly 40KTS. We also discussed contingency plans if the engine needed to be shutdown or just failed outright. Basically if we needed to secure the engine anywhere before the 500 foot call we would go around as necessary and complete all procedures in accordance with the QRH and FM. Below 500 feet we would continue to a landing unless we had a compelling safety reason to go around. We landed uneventfully and cleared the runway. The engine ran normally the entire flight and for nearly four hours with the oil quantity gage reading zero (but with otherwise normal indications except as detailed above). Once clear of the runway we shut down the left engine. After shutdown the left engine oil quantity read 1 quart. With respect to communication difficulties. This particular fleet as you are aware is our oldest fleet and has had many systems added at various times to the cockpit that weren't part of the original design. (For example; CPDLC; SATCOM; WiFi; etc). There have been many innovative engineering solutions to fit all of these upgrades into a cockpit that never envisioned these systems. Unfortunately this approach does nothave the unified design of modern communication panels and limitations that are aircraft specific within this fleet. In order to place a SATCOM call in this aircraft type it is required to flip a switch on the ACP (Audio Control Panel) to select SATCOM vs. HF. There is no multiplex / multi channel capability. During our turn back we received several SELCAL from ZZZZ RDO relaying ATC instructions. Each time we had to stop the SATCOM call with Dispatch and Maintenance Control to switch back to HF to answer ATC in a timely manner. Then we would have to switch back to SATCOM and reestablish the call and continue the conversation. Had this been a more dire or time critical problem that lack of communication ability may have a direct impact on the outcome of the event being successful or unsuccessful. It also defeats the purpose of and adds confusion to the delegation of duties between PF; PM; and relief pilot. In this specific instance the FO that I transferred aircraft control and routine ATC com to was stymied and ineffective; through no fault of their own; in doing the tasks that I assigned them. It required me to stop managing the problem and reconfigure the radios to allow basic communication with ATC. Again in a different type of situation this could have significant consequences. If we intend to keep these aircraft longer than expected; and the use by" date seems to be getting extended further and further; may I suggest we replace the ACPs with a more modern variety that is used in the other fleet and solve the single channel problem.With respect to Wi-Fi. We are provided with modern tools to improve our ability to manage the complex environment we routinely work in. Unfortunately those tools rely largely on a usable data connection to leverage their potential. Also unfortunately; the WiFi in the cockpit is largely useless a significant portion of the time. This is directly related to signal strength and NOT overall internet connectivity. It is usually the case that; while not great; there is passable data available in the cabin and sporadic or unusable connectivity in the cockpit due to having a signal strength that sits at a single bar. While I remember the days of LDOC (Long Distance Operational Control) through a radio operator; that simply is not efficient or part of our modern workflow. In this specific instance there were literally a dozen airports that needed to be reviewed to know with reasonable certainty that our divert plan was viable. It would have been nice if ANY of the iPads in the cockpit could have connected to a data source so that could have been a coordinated effort with Dispatch and managed efficiently in flight. Instead we had to communicate via text mostly; because of SATCOM limitation described above; with Dispatch and then ask for or wait for weather data to be uploaded and reviewed. The data arrives piecemeal and oftentimes out of order further complicating analysis and use. A simple signal repeater inside the cockpit door or very near the cockpit could solve this problem. The other alternative; when faced with a divert decision; would be to just proceed to the listed alternate with minimal analysis. In this case that would have resulted in a safe but sub-optimal solution that would have complicated recovery in both time and resources used.The next day we conducted a thorough debriefing of the event as a crew. Here are some key takeaways:1. Identify and define the problem / situation correctly. (Communication; Planning & Decision Making). Initially we thought that an engine failure might be more imminent but after discussion we arrived at a different conclusion that the engine might run for a long time even with zero oil quantity indicated. And in fact it did. 2. Setting the tone was important. It focused us all on managing the situation based on the facts that were known. (Leadership Effectiveness)3. Advocacy and crew input. Both FO's are highly experienced professionals that offered opi"