winter additive for fuel?

depends on how long the fuel is sitting in your tank. i only pump 3 gallons at a time, so i don't exceed the 6 month pip interval.
i think prime is a year. if you are going to exceed that, you don't need a winter additive, you need a fuel stabilizer like stabil

 

Isopropyl alcohol gas "dryer" in the red bottle is what you want to use. It mixes with water in the gas and that absorbed by ethanol and allows it to be burned n the engine with combustion.

You do not want to use methanol in the yellow bottle as it will not mix with water. It just "floats" above the water, which settles at the bottom of the tank. If you run near empty, a "slug" of water taken into the fuel pump will likely cause the engine to stall, and water, unless mixed with isopropyl, will not burn.