A fairly new snowblower of mine had gas left in it over the summer. Before the first snowfall of the following winter it would not start. A dissection of the carburetor revealed numerous places where small passages were completely filled with a sticky gummy substance that had to be mechanically removed. After cleaning and reassembly, it fired right up with fresh gas. Maybe the old gas would have worked just fine once it could flow. Clearly having the gas sit in there had adverse effects.

[delayed]

Fuel stabilizer is cheap insurance for anything that overwinters with fuel in it -- motorcycles, boat engines, etc.

You have to put in in the tank and run it for a bit to make sure that the carbs don't have untreated fuel inside.