B767-300 and 300 ER
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Troubleshooting
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Diverted; Flight Crew Landed in Emergency Condition
Aircraft
FL350 in ZZZZ airspace with clear weather.  The Captain (Pilot Flying) noticed the number one engine oil quantity display showing zero. The number one oil pressure had dropped to 19. The oil temperature display was showing 158 and rising slowly. The First Officer (Pilot Monitoring) pulled out the QFE to determine the appropriate checklist to run. The captain noticed the oil temperature display turn Amber; reading 160. The crew elected to run the checklist for high oil temperature. The Captain turned off the auto throttles and brought the number one thrust lever back to idle and began to initiate a single engine enroute descent. The Relief Pilot began communications with Dispatcher via ACARS as SELCAL was inop. First Officer coordinated with ATC for a divert to ZZZZ1. [Priority was requested] with ATC. The plane was flown in VFR weather to ZZZZ1 for an uneventful 20 flap single engine landing on Runway XXR.
About 3 hours into the flight; as we approached [the] airspace; and were talking to a ZZZZ controller; I noticed the number one (left) engine's oil quantity was indicating zero (0). I immediately checked the oil temperature and pressure and at that point in time they matched; almost exactly; the right engine's indications. I then asked the First Officer to get the QRH out for zero oil quantity indication...for which there is none.As the First Officer dug into the QRH looking for a procedure that did not exist (zero oil qnty). the oil temperature started to rise and the pressure to decrease. That was when the First Officer and I looked at each other and I asked for the High Oil Temperature Checklist. Simultaneously; I immediately brought the engine back to idle and started talking divert. The Relief Pilot was in the cockpit at the time and looked over my shoulder as I looked at the NAV display for available airports and also at the closest airports (alternate page on the FMS) and saw that ZZZZ1 was about 50 degrees to the right and about 320 NM and indicated the closest on the Alternates page. I will admit that my mind was leaning to go to ZZZZ1 almost right away since I know it has two long runways; is low in MSL field elevation; and has good ground/ATC support; I also knew since it was early in the day that thunderstorms would not hinder our arrival and approach/landing. In fact; the field was wide open with light winds; few clouds and excellent visibility. As we looked for divert airports; we asked ATC for lower since we were at FL350 and the single engine out page indicated that FL215 was the recommended altitude. I selected engine out on the FMS when I pulled the throttle to idle and we began a very slow drift down to FL200 (requested FL 200 from ATC and we [requested priority] at the same time); the initial engine out speed was 253 knots which I edited to 290. (After selecting Engine out of the FMS I then selected MAX CON on the thrust and set the right throttle to match the max continuous max thrust indexes). I must admit that the drift down was very controlled and actually quite slow; that was nice to know. With 320 miles to go to ZZZZ1; which is what we agreed upon as our divert airport; I actually had to go to idle and boards as we approached the field from the east; northeast; in order to get into the visual pattern for the Runway XXR ILS/Visual approach. We had A LOT of time to prepare and brief all contingencies and the First Officer and Relief Pilot were exemplary in their duties. The Relief Pilot did perform a fuel balance about 150 miles from ZZZZ1. The throttle was kept at idle the entire time from when it was first brought back to idle and the oil temperature peaked at 167 degrees and then decreased as time of flight (since the beginning of the divert) to ZZZZ1 increased and altitude decreased. Oil pressure went as low as 19 psi; but never lower.I did perform a precautionary S/Engine approach and landed with flaps 20 at 320k G/W and an approach speed of 160 knots. Stopping was not a problem; though Tower asked us to turn off at the end. A fire truck followed us to the ramp and the left engine was secured after turning off the runway.[The cause was a] major loss of engine oil in the left engine. Nothing contributed to this other than an unknown (to us) oil loss and subsequent divert.
Air carrier flight crew noted low oil pressure and high oil temperature during cruise on Number 1 engine. Flight crew followed QRH and diverted.