The 20 pounders from a grill will work, as will the larger 100 pounders and up. As long as you don't draw to much from them at any one time. A little buddy heater is OK hooked to a BBQ tank, a 150,000 BTU furnace is not.
But those little one pound canisters are pretty helpless when the temperatures drop. If you bring the canisters indoors to warm up before taking them out to use in the little Mr. heater, you'll be OK. But if your storing the one pound canisters outside in the 20 below zero weather, they'll fire up for a few seconds, and then as the pressure is bled off, the heater will quit. You can get the pilot light lit, but as the catalytic burner comes on, it glows for a few seconds and then winks out.
The people that heat their houses with propane will usually have a 500 gallon or larger propane tank to ensure adequate pressure and volume to the household furnace during those cold spells.
Cold temperatures are hard on everything. Number 2 diesel at 35 below zero attains the consistency of bacon grease at room temperature. About the same color too. Kind of a cloudy milky white. At 40 below zero, you can stand on an oil drain pan with 80/90 weight hypoid oil in it and just leave boot prints. You won't sink to the bottom.
I heat my house with electric and have a fuel oil backup furnace. I have a 275 gallon tank of fuel in the basement, because if it was outside, the fuel would never flow through the feed pipe in cold weather. Keeping it in the basement allows me to burn number 2 diesel. If the tank were outside in the cold I would have to use number one diesel fuel in order to get it to flow. Number one costs more.
I use number one diesel in the tractor for snow removal but I only go through 25 gallons or so through the winter months. When the number two diesel gets cold, the waxes precipitate out and plugs up the fuel filters. And there you sit until you swap out the filters and dump a bunch of additive into the tank to dissolve the waxes. An all around pain in the butt at 15 or 20 below and the wind blowing. Spend the few extra dollars and burn number one.
Many, many years ago. Before the advent of modern ignition systems. If conditions were just right. A super cold night and then a warm front would move in in the morning. The engines (gasoline in cars, trucks, airplanes and tractors) would draw that warmer air in on the first crank of the starter and the moisture in the air would condense on the spark plug electrode because it was colder from the night before.
Now a warm front moving in just means that the temperature has gone from a neg 40 to a neg 10. Enough of a change to cause condensation on the spark plugs, but not warm enough to make pulling and drying out spark plugs on an engine a fun time in the morning. Luckily it was a rare occurrence that didn't happen every year. Since then, better ignition systems, block heaters and heated garages have made this almost a thing of the past.
This is all old news for the folks in Canada and Alaska. On the other hand, we don't run into hot weather vapor lock very often either. But, better engineering and fuel formulations have pretty much eliminated that too.
