by Phil » Mon Sep 12, 2016 6:07 pm
At sea level and 70 degrees F, you get about 1 hour of burn time out of an 8oz isobutane canister. That's the environment in which they measure stove and fuel performance. For practical purposes, in colder temps, cut that time at least in half, especially with cooking fish. Plan your meals as they relate to fuel use: number of people, number of meals per day, volume of water required to prepare the food and drinks, and give yourselves about 20% more on the conservative side. For my stoves, I usually calculate about 8-10 minutes of run-time per liter boiled, and find that to be generally realistic. Bring 4 canisters and split the load. If you have extra, oh well.
Canisters are usually a mix ratio of 80/20 isobutane (<2% n-butane) to propane. It's a little bit confusing at first, and all very esoteric, but cold temps are boiling points, not freezing points: the point where the fuel will no longer convert from a liquid to a gaseous state. Propane has a lower boiling point (-44F) than butane (31f) and isobutane (11f), so if it's below freezing, your stove will only burn the propane and none/almost none of the other gases. But, for every 1000 ft of altitude gain, and lower outside air pressure that comes with it, the performance of the fuel types will allow you to lower the above limits by about 1 degree F. Besides keeping the canisters warm at night, and even if you don't, if your stove and/or fuel line allow it, invert the canister while the stove is running. That way you go from a pressurized system that requires liquid fuel to vaporize, to one where the liquid mixture is fed by gravity, and you won't get canister fade or complete failure. The result will be better fuel efficiency and a completely empty canister when you're done. It also helps to be more patient and use a lower valve setting than full-on roaring jet engine mode. And one other trick is to use a wind screen or rocks piled up in order to keep the canister warmer as the fuel inside it is depleted.