The right fuel in the right amount is ultimately important for success on your outdoor trip - and sometimes for your survival. Buy the right quality and you are more secure that your burner does not soot. You are also sure that you use only a low amount of gas per meal and therefore you don't have to carry too much on your trips.
Primus, among others, have introduced gas for use in summer and winter and sells it together with their all-round gas. But what is the difference? The individual gases are optimized for use at different temperatures, and therefore you use less gas in the individual situations. Primus' winter gas also has a membrane in the top part of the gas can - where the gas comes out. It allows you to not have to sit and warm the can in order to get optimal combustion.
Maybe you have tried with an all-round gas of good quality, that you have to sit and warm the can when the temperature is around freezing point, in order for the gas to burn optimally. You don't have to do that with Primus' winter gas, which burns optimally without having to keep the can warm.