Thanks for all the info guys. I guess what I am hearing from you is that pure butane as recommended in the instructions is not so good at low temps, that a propane mix is better at low temps, and importantly is a mix of 35% propane okay to use despite the instruction manual saying max 30%?

I am wary of using an external gas bottle for starting, though I recognise the benefit of it being able to maintain gas pressure much better than the small on-board tank. The reason I am wary is that when I disconnect the tube for filling the tank, the gas/liquid pressure in the tube between the main bottle and the one-way valve bursts out. That is safe when nothing is running but is it a potential fire/explosion hazard when the engine is running?

H.