What about below 0°F/-18°C? Remember the three basic rules of gas stoves in cold weather: choose good fuel, start with a warm canister, and keep the canister warm. Those rules still apply, but in extreme cold, they become critical. You must have a "warm" canister (generally about twenty degrees above the boiling point of your fuel) for your stove to work. If things go seriously wrong on a backcountry trip and you can't warm that canister, you're in a world of hurt.
Hey, wait a minute. So, why even bother with gas? I mean if I can't warm up that canister, then I could die, right?
Yep, you could die. That's not an exaggeration. This is not something to take lightly. But there are reasons to want to take gas in extreme cold. One reason is safety. If you have to cook inside your shelter, gas is the safest option. Yes, I know, stove manufacturers unanimously proclaim "never use a stove inside." Let's see. It's -5°F/-20°C. It's blowing hard out there. There's snow everywhere. It's basically a white out. You're going to go outside to cook? Really? There comes a point in time where cooking inside is the lesser of two evils. Cooking outside might mean certain death whereas cooking inside while risky is far safer. Yes, you have to worry about fires. Yes, you have to worry about Carbon Monoxide. But you're a complete idiot if you try to cook outside in a howling gale when it's -5°F/-20°C out.
Back to my point about safety: Gas stoves generally do not require priming. If you know anything at all about priming a liquid fueled stove, you know flames can spring up several feet into the air. Yes, with practice and care, you can keep the priming flames smaller. In ideal conditions. But if you come stumbling into your tent at night, half dead, half hypothermic, with hands about as nimble as a block of ice, just how controlled do you think that priming will be? Priming inside a confined space with flammable items surrounding you is just not a good idea. With gas, you just open the valve, light, and go.
Another issue is mechanical reliability. Pumps on liquid fueled stoves can and do fail in extreme cold. While the valve on a Gas canister can jam, jams are far less likely than on liquid fueled stoves, and the valve usually jams open. In the case of a gas canister with the valve jammed open, just leave the stove attached to the canister. Hardly ideal, but leaving the stove attached will allow you to use the stove's valve to hold back the gas – and you can still use the stove.
Now, even though I have called out liquid fuel pumps as having reliability problems in extreme cold, that is not to say that such pumps are unreliable per se. In other words, most liquid fuel pumps will do fine, but failures do happen and they happen at a higher rate than with gas canisters.
Me personally? I'd take both. Yes, I am serious. I'd take a liquid fueled stove and a gas stove both if there were any way my team could reasonably manage it. I'd take more than two stoves if the group were large enough to support it, even if I thought we could get by with less. Gas will be safest if you have to cook inside, but if you get into a situation where you cannot warm the canister (a distinct possibility in extreme cold), you still have a liquid fueled stove. In extreme cold, it's time to quit counting grams and stay focused on coming back alive.
For your liquid fuel, use kerosene not white gasoline. Kerosene is much less likely to start a fire if there are any leaks or spills. White gasoline is volatile stuff and really shouldn't be used inside unless you just don't have any other choice. I'd also bring a spare fuel pump (or two) and expedition type maintenance kits and tools. In extreme conditions, take extreme precautions.
In extreme cold, the real failure is the failure not to have everyone come back in one piece.
P.S. OK, so maybe "bring both" is a little bit of a cop out. If I absolutely had to choose only one stove for extreme cold weather, I'd probably go with kerosene. But I really would seriously consider bringing both a liquid fueled and a liquid feed canister gas stove, especially for a group. You just don't want to screw around when it gets that cold.
Related articles and posts:
- Cold Weather Tips for Gas Stoves
- What's the Best Gas for Cold Weather?
- Gas Stoves: How Cold Can I Go? <==Most comprehensive article on canister gas and cold
- Canisters, Cold, and Altitude: Gas in a Nutshell
- Canister Stoves 101: Thread Care
- Gas Blends and Cold Weather Performance. (Why not just use propane?)
- The "Super Gnat" (Camping Gaz or threaded canisters with one lightweight stove)
- Backpacking Gas Canisters 101
- Gas in Extreme Cold: Yes or No?
- Gas in Cold Weather: The Myth of "Fractioning"
- Stoves For Cold Weather I (Upright canister stoves) – Seattle Backpacker's Magazine
- Stoves for Cold Weather II (Inverted remote canister stoves) – Seattle Backpacker's Magazine