The best cure for deterioration of fuel during long-term seasonal storage is to drain the tank and carburetor bowl. There's not much gas involved so I usually siphon / drain into a fuel can and blend into my car's tank. That way you avoid harmful byproducts from oxidation, water absorption and even microbes introduced as the gas tank breathes air in and out through daily temperature cycles.
There are many "snake oil" additives out there claiming to be the magic cure to perceived E10 problems like gum and varnish formation, corrosion and phase separation with absorbed water. It's best to read the MSDS to see what you are paying for. Many contain just a simple stoddard solvent (naphtha) or isopropanol and have little more than a placebo effect.
There's a good summary here:
http://www.fuel-testers.com/is_gas_additive_safe_with_e10_list.htmlBottom line, get fresh Tier-1 gas from a station that has a high turnover and you will be fine if used up in a month or two. Otherwise, at least drain the carb bowl with the little screw at the bottom - it's a simple enough precaution.
There's another ethanol problem, namely increased formation of intake valve deposits. So I blend Red Line SI-1 or Chevron Techron concentrate in all my vehicles periodically to counter clean these deposits that are especially troublesome if you have fuel injection. These additives contain PEA or poly ether amine that is proven to be effective and is already in Tier-1 gasolines like Chevron and Shell.
You can read more about the Red Line tech here:
http://www.redlineoil.com/content/files/tech/S1-1%20Tech%20Info.pdfCheers,
RR