> I often hear that the XGK is better in extreme cold than the Simmerlite and I'm trying to understand why.
Well, both have a preheat tube right in the flame to vaporise the fuel, so both 'should' work.
However, the Simmerlite is a quiet, respectable 'silent' burner, while the XGK is a raving extraverted machismo noise machine. Perhaps it is partly a mater of perception: the noisier the better?
And don't forget the priming instructions which come with the XGK: it should look like a football sized fireball. Yeah, seriously, that is in the MSR instructions! This approach may help get the XGK going faster and better.
I am not sure one will work much better than the other in reality if properly primed, except that the XGK can handle all sorts of fuels while the Simmerlite really only likes white gas.
Why the difference? It has to do with the jet size, the air flow arrangements and the type of burner used. High up in the mountains, or deep in the Antarctic, sometimes all fuels are a bit like kero! It may also be that the whole XGK gets stinking hot, while the open light Simmerlite does have parts out of reach of the flames which can cool down a bit.
The Powermax canisters should work down to -25 C (-13 F) by themselves. Below that the internal pressure is less than 1 atmosphere, and the gas does not come out. But as soon as you warm them a bit (cold liquid water is fine), they will rev up.
Coldest? Dunno. Not quite that cold. Thank you!