gas stoves - fuel mixture

[johnct]

Just bought a new gas stove, Soto WindMaster. The staff in the shop were saying that the best fuel mixture is 80/20 Isobutane/Propane, especially once you get above sea level, and that this is better than 70/30. I bought a Jetboil canister which they said was 80/20 (though the canister doesn't indicate the proportions). However on reading the instructions it says ""this appliance shall only be used with butane 70% / propane 30% gas canister...7".

Does it make a difference to the stove's operation which mixture I use? Both from a safety and a performance point of view?

[Mark F]

The three gasses that are found in disposable canisters are butane, isobutane and propane. The key aspect of gasses which may affect the operation of a stove is the boiling point of each gas.
See http://bushwalkingnsw.org.au/clubsites/FAQ/FAQ_GasStoves.htm for far more information that you really want about stoves and gasses. The important aspect of the behaviour of gas blends is that the gas with the lower boiling point will be burnt off first leaving the gas with the higher boiling point making up an increasingly greater percentage of the remaining gas mixture. The effect of this is that a stove is being used in temperatures near the boiling point of higher boiling point gas it will start to work poorly as the lower boiling point gas is preferentially consumed. This can be controlled by using a stove that can handle the canister being inverted (not the stove you have purchased).

Returning to your questions. Ignore the instructions - the stove will work perfectly well with any compatible canister provided the temperature is warm enough. If your use is 3 seasons in most of Australia you will be fine with any compatible canister. Efficiency-wise there is really no practical difference between gasses - efficiency comes from running the stove at moderate to low levels so the flames are not escaping up the side of the pot and using a windscreen (with care) especially if it is breezy.

The shop staff are equating "above sea level" with colder temperatures so they are half right. As you rise above sea level the boiling point of the canister gasses (and water) decrease allowing the stove to operate with the same gas mix at colder temperatures, so it is a tradeoff between the altitude and the temperature.

[Strider]

I wouldn't have though ANY mixture would be much use below sea level

I use the Jetboil canisters because they contain more n-butane, which has a lower boiling point than regular butane (-11C versus -1C).

[corvus]

I use Elemental (Kovea ?) Gas and have no problems upright or remote also have a couple of adaptors to run the Spray Can type in Warmer weather also upright or remote

[Orion]

I wouldn't have though ANY mixture would be much use below sea level

I've used my canister stove in Death Valley.

I use the Jetboil canisters because they contain more n-butane, which has a lower boiling point than regular butane (-11C versus -1C).

I buy those ones too. But they're better for the cold because they contain isobutane instead of n-butane. The "n" in n-butane stands for normal.

[Strider]

I use the Jetboil canisters because they contain more n-butane, which has a lower boiling point than regular butane (-11C versus -1C).

I buy those ones too. But they're better for the cold because they contain isobutane instead of n-butane. The "n" in n-butane stands for normal.[/quote]
Sorry, that's what I meant!