[BenjiWiebe]

The reason diesel doesn't usually gel is that, starting in the fall, fuel stations/refineries start adding anti-gelling agents to the diesel.

If you have "summer diesel" in your tractor during a cold spell, it will gel. And a block heater won't help, since the fuel gels in the fuel lines and tank too. And trying to start the engine pulls in that gel into the fuel filter and sort of strains the chunks out, causing your fuel filter to need to be replaced even once it's warmed up.

I'm not sure at exactly what temperature it happens, but a Kansas winter will typically gel summer diesel at least a couple of times.