B747-400 Captain reported oil quantity was low and decreasing on #2 engine. The Flight Crew was advised to return to departure airport for additional maintenance. The Flight Crew conducted an air turn back and dumped fuel prior to landing.

Narrative

Aircraft X came from ZZZZ1-ZZZZ. It had been in ZZZZ1 for a heavy check. I was Captain on the crew for Aircraft X; scheduled to operate ZZZZ-ZZZ. The plane was late arriving into ZZZZ and the inbound Captain briefed me on their issues. When they had started the engines; #2 oil quantity dropped from 19 before start to 10. They blocked back in and took a delay while Maintenance addressed the issue. Second time they started it dropped from 19 to 14 after start; but the other engines were all at 15-16 after start; so they continued. After takeoff it was at 10 and they got the status message for low engine oil quantity. There is no checklist for that. They called Dispatch and Maintenance and decision was to continue to ZZZZ. Oil quantity was at 7 by the time they got to ZZZZ. My crew and I were waiting when they arrived. Maintenance worked on the engine while we waited; including two engine runs. They capped a line and put it on a non MEL. With the logbook signed off and; theoretically; the issue fixed; we pushed back. The engine #2 oil quantity was at 19 when we started; 14 after start; and 10 after TO (Takeoff). At top of climb it was 9. After top of climb I sent Dispatch a message with all the info and received a 'copy' reply. I discussed the situation with my FO (First Officer) (third pilot was already in the bunk); we reviewed the QRH for high oil temp and low oil quantity; reviewed the FOM guidance on an inflight engine failure or precautionary shutdown; and continued on. Over ZZZZ2 we receive a message from Dispatch; 'Request return to ZZZZ for Maintenance; stby for reanalysis.' I replied; 'Confirm you want us to return to ZZZZ.' Get the reply; 'affirmative'. So called ZZZZ3 on the VHF and requested change of destination from ZZZ to ZZZZ. Got a 'standby'. After a few minutes a different controller on the same frequency called and asked us to verify the change in destination and return to ZZZZ. Confirmed that request with them; then got another 'standby'. The next call was asking why the request to return. Told them company request for maintenance. They asked if we wanted to declare an emergency. I said no. They asked if we needed assistance. I said no. Then they issued a heading to initiate our return to ZZZZ. At this point the oil quantity was down to 7. We got an ACARS from Dispatch; 'Maintenance Control requests you reduce power on engine #2 to idle.' So we requested lower from ZZZZ2; got cleared from FL330 to FL240; which was well below our engine out drift down altitude; selected the engine out VNAV prompt; turned off the auto throttle and pulled #2 back to idle. We received a reroute from ZZZZ2 Control; plugged it into the FMC and updated Dispatch. We were estimating landing with 63;500 kg of fuel; which would have put us 19;600 kg over max landing weight (and that's if we flew the full arrival; which we never do in ZZZZ). We were burning approximately 15;000 kg/hr so were looking at holding for around 1:20 or dumping. At this point we were approaching the FIR with ZZZZZ; so decided to wait until their airspace to request the hold or dump. The oil quantity had stabilized at 7 after pulling the engine back to idle; so we weren't immediately concerned with it going to zero and potentially causing severe damage and possibly seizing. Had another back and forth with ZZZZZ about the reason for the divert; was it an emergency; did we need assistance; etc. We told them it wasn't an emergency but needed to either dump fuel or hold for 1:20. They asked how long we needed for dumping. We told them; approximately 25 minutes. They said; 'fuel dumping approved; advise when complete.' Started dumping at FL240 over the [ocean] and finished a couple minutes prior to the way point ZZZZZ1 in the descent to FL180. Once we had the fuel dump going; had the FMC set for approach and arrival; and all the big stuff covered I woke up our third pilot; updated him on the situation and asked him to be a third set of eyes and make sure we didn't mess anything up. Got performance for a max weight landing; briefed everything; ran the descent checklist and from then it was just like a 3 engine approach in the sim. I was Pilot Monitoring on the leg and continued in that role; managing the situation while the FO (First Officer) flew the whole time. He did a great job staying focused on that. Approach and landing was uneventful. Landed at approximately 301;000 KGS (max is 302;092). Both the ZZZZ2 and ZZZZ ATC Controllers were excellent; the crew I was with did a great job; and our Dispatcher was fantastic.Low oil quantity indication on engine #2. History of that issue on previous flight with Maintenance having worked to solve the problem in both ZZZZ1 and ZZZZ. Decision by Maintenance Control and dispatch to do an air turn back and return to ZZZZ rather than continue to ZZZ. Crew was in agreement with this decision as it seemed a safe and prudent choice. Jettisoning fuel was a crew decision. We were able to complete the jettison during the return to ZZZZ without having to hold or delay the arrival. Jettisoning allowed us to make the landing below the max structural landing weight.I will be appreciative of any feedback regarding what I as the Captain and we as a crew could have done better. I appreciate that the issue was previously addressed by Maintenance in both ZZZZ1 and ZZZZ. When we left ZZZZ the issue had been addressed to the best of the Station Mechanics' ability and I am sure they; like we; thought it was fixed. That turned out not to be the case; but having watched the effort taken by Maintenance in ZZZZ; I am confident they did due diligence. I appreciate the briefing by the inbound crew. I appreciate the conservative decision by Dispatch and Maintenance Control to do an air turn back. I appreciate the coordination by both the ZZZZ2 and ZZZZ Air Traffic Controllers. I appreciate the excellent CRM and flying skills my First Officer who did an outstanding job as Pilot Flying throughout the incident; as well as the support from our third pilot in the observer's seat. Lastly; I would like to thank the Company training department. This event; while non-routine; was handled without stress or difficulty because of our engine inoperative training in the simulator and practicing diversions during RLOFT scenarios in the simulator as well. I am sure there are things I could have done better; but overall am satisfied with the decisions that were made and outcome of events.