It doesn't matter where you live in the North America, there is a risk of diesel fuel in farm equipment and trucks gelling during cold spells. Yes, refineries switch to "winter grade" diesel fuel starting in October, and yes, winter grade fuel helps reduce problems with gelling when temps drop below 30 degrees. But if you want to make absotively, posilutely certain that your diesel engines keep running no matter how cold it gets in your neighborhood, here are some tips:
-if you're using bio-diesel, whether soy oil-based or vegetable oil-based, the general recommendation is to NOT store vehicles more than a month with bio-diesel in the tank. Most manufacturers recommend flushing at least one tank of petroleum diesel through the system, and storing machinery with petroleum diesel in the tank. I'm not bad-mouthing bio-diesel--I'm just saying that even proponents of bio-diesel recommend that bio-diesel be kept "fresh."
-winter-grade #2 diesel is usually okay down to 30-degrees. Yes, it is rated for colder than that, but why risk problems?
-If temperatures are going to drop below 30-degrees F, start adding some type of anti-gel additive. Read labels carefully and add at recommended rates. If fuel has already started to gel, it's too late to add anti-gel. It has to be added and mixed while diesel fuel is completely liquid.
-there are products that are labeled to un-gel diesel fuel that has already gelled. I've never used those products--you're on your own.
-I've heard of people adding small amounts of gasoline or kerosine to their diesel fuel to "thin" it. Don't do that. That "old farmer's trick" could severely damage your engine. Just because Joe Blow got away with it doesn't mean you will.
-if the weather is going to be -10 and colder, it's best to start blending #1 diesel fuel with your winter-grade #2 fuel. If the weather is going to be consistently below zero, it's not a bad idea to run pure #1 diesel fuel.
-if a engine has gelled and you need to limp it into a shed, our trick at the dealership is to fill a five-gallon fuel can with room-temperature, winter-grade #2 diesel treated with anti-gel. Rig a suction hose and run it from the fuel can to the intake side of the fuel filter. Change the fuel filter (it will be full of waxy, gelled fuel). Fill the new fuel filter with room-temperature diesel fuel, hand-prime the fuel pump, then see if the engine will start. If it does, head for a heated shed, and get there before you run out of warmed fuel, or that warmed fuel gets chilled.
-there are many ingenious tricks to get gelled engines started, but it's best to plan ahead and avoid the problem in the first place. Been there, done that, didn't enjoy myself.