Flew an old knackered 737-700 the other day. The flight plan fuelfactor was 0,0 %. The next day I had the sister ship, from the same era, with a fuel factor of 5,0 %
I take the FMC fuel prediction with a pinch of salt as, in my experience, it significantly over-estimate fuel on arrival even when the winds aloft have been loaded and the time prediction turn out to be fairly accurate.