Hello again, another question, sorry.

Its been a very harsh winter here.

Should I be using a bit of gas tank Antifreeze each fill up, or 2nd fill?
If so what is a good brand to use, or does it matter?
Is whatever they sell at the gas station fine, or no?

 

How cold is it exactly? I think this is usually an issue with diesel but not gas cars I think, though if it gets cold enough I suppose it could be ap roblem.

 

We were at -30 to -40 for weeks, its now warmed up to just -10C.

My concern is water, both condensation and from the gas station.