According to :

I have a neighbor with oil heat. He has a diesel farm tractor. He
always drains fuel from his tank for the tractor. It seems to run ok,
but he's always complaining about gelling in severe cold weather. I'm
not sure if it's because he uses that heating oil, or just a common
problem with diesel engines in general. I know truckers are always
adding stuff to their fuel in winter. This is one reason I wont buy a
diesel tractor. I'll stick with gas.

It's a common issue with diesels. You just have to know about it.
Regular "summer weight" diesel begins to gell/freeze at IIRC,
a few degrees _above_ zero F. "Winter weight" goes to at least -35F.

A oil heat tank that's indoors, buried, or fairly well sheltered will
freeze a lot later than a fuel tank suspended in the wind like in a
tractor. The long and the short of it is that you have to pay more
attention to what _weight_ of diesel you're using in a tractor or
truck than in a oil heating tank in the winter.

Decent modern diesel engines don't care too much about temperature
_provided_ you're using the right weight for the season.

Heck, the Polaris Mine (Little Ellsmere Island, northernmost mine
_ever_ built) used diesel vehicles _exclusively_. Toyota diesel
pickups. Never shut them off unless they were in the garage for
an oil change ;-)
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.