They all are - essentially there is little difference between most modern blends which are mostly butane, with a little bit of isopro and propane in them to increase cold weather performance.

the trick is that the gases don't actually "mix" - the butane is still butane, and is liquid (read that - no gas comes out) at 4 degrees centigrade - the little bit of isobutane and propane is to give the stove soemthing to burn that will come out at colder temperatures, and hopefully warm up the canister enough that the butane will gasify.

Of course if it's cold enough and you burn off that little but of stuff before the canister warms up enough - it really doesn't work very well so in the cold you may need to warm it up in your hands first, or keep it in your sleeping bag for best performance - practically they do pretty good in my eperience down to about -5 C - after that they get tempermental. So for me, I use them for "three season" trips.