Gelled up or Froze up?
Living in Wy and travelling the cold states in the winter has given me some real lessons. Once the weather turns most, and I say most diesel is blended in cold climates. Some lubrication additive is not a bad thing for a blend, however here the stations are serious about keeping their diesel gell free and additives added so I don't feel the need locally. When travelling I always ask what the diesel is good down or if they have a POP(point of purchase) and decide from there. Better safe than stranded waiting to thaw.
However, the only time I thought I had a gelling problem, in Minn. from a major truck stop I picked up contaminated fuel last Jan at -5F. Well it turned out nothing I could buy from Wally World or any supply house would cure the crude and I mean crude. Brown muddy stuff from the water separator, poor mileage, and performance. This was after a filter change also. I'm not sure what was going on in the tank, water or something growing or what but nothing helped. Then I found stuff called KD-100, just like the guy said, completely eliminated the problem in 1 tank full, completely!! I'm impressed with this stuff to the max.
Anyway the point being you need to carry emergency deicer for the fuel as well as somthing like KD100 to eliminate other contaminates and especially condensation which I think is a real problems in the winter. Be Prepared.