I am nearing the end of an Atlanta to Moscow flight.  Although the FMC was reporting insufficient fuel at the beginning, now it is saying I will have plenty.

My recommendation is to plan wisely, ignore the FMC and just find out if you run out of gas or not.  It is a sim.  I am using the freeware 767-300 planner originally put out for the other 767 and it works fine.

EDIT: landed with 33,600 lbs of fuel left (16,800 kg), which is too much; I should have stuck to the recommendations of the fuel planning program.  I had wing tanks full, 75% in the center.  I don't think this bird has short legs at all.  That was right at 5000 nm.

Actually the whole flight was flawless, and she was rock steady during cruise and on final.  Very, very well done Captain Sim!  This is a delightful airplane and as good as any as I have ever seen if she keeps giving me flights like this.