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Hi, something cool happened to me, but I don't know whether it's a simulated failure or rather a simulation failure. I was going on a trip from RJAA to SBGR, so I selected the JAL 77L with 3 auxiliary tanks. I know that in reality, there are no 77Ls with 3 aux tanks, but there's also no service from Tokyo to Sao Paulo... Anyways, I took off from Narita and about 2 hours of flight time, well shortly before I would arrive at the outermost of the Aleutian islands, I got an EICAS message saying "Fuel Disagree". I noticed that I really had considerably less fuel than expected (the aux tanks were already completely drained). I was quite thrilled and brought up the ECL -> Fuel Disagree Checklist -> Fuel Leak Checklist. There was no fuel leak that I could detect, and so the plane wanted me to "use the more accurate value" of Totalizer vs. Calculated fuel quantity. Now I wondered which to choose. Judging from the hours flown so far, it had to be the calculated value, judging from the content of the tanks as displayed on EICAS, it had to be the totalizer value. I figured out I'd go with what the aircraft showed me, and I "cheated" a bit and took a look at the fuel quantity under "FS Actions" on the center FMC, and also in the W&B menu of the sim, and they all agreed with the totalizer value, which was about 30,000 lbs less than the calculated fuel. After selecting the totalizer value, a quick look at the Progress page revealed that I would have no more than 1900 lbs of fuel left in Sao Paulo. So I turned the aircraft around and flew back to Japan, a 21-minute fuel jettison included, and safely landed in Narita. Of course I researched a bit, and I found out that a) Boeing warns about this Fuel Disagree issue on the real plane (FCOM 1), and b) there have been simulation related issues of this kind back in 2013 and 2015 (Avsim). I wonder what was the cause of my failure. It never happened before and I did pretty much everything as I always do, the only difference being the fact that I entered the fuel value selecting "100%" instead of entering a number, since I had to use every bit of fuel possible. Upon taxi, I remember that everything seemed normal to me, but shortly after takeoff, I recall switching off the Aux Fuel Pump comparably early, i. e., compared to the one other flight where I needed it. Could I this be a simulation issue, or is it a PMDG feature? If it's a PMDG feature, what was the simulated effect of having suddenly lost 30,000 lbs of fuel? I couldn't detect a fuel leak monitoring the wing tanks for over half an hour, and there seems to have been no drain afterwards.