All gas stations change gas from season to season. If you have the summer gas in the winter when it is very cold, your car/truck will not start good at all. The winter gas helps this but isn't good for emissions in the summer.
Ya there is also the fact the in some parts of Canada and all of Alaska the temp changes 80+ degree from summer to winter.
Try starting a car at -75 degree with summer fuel..The damn gas will almost gel on you with the additives in it. In the winter they use diesel at the oilsand plants that burns 40 to 50 times hotter then the jet fuel use in a fighter. They use it their heavy haul trucks.
