How long and where is it going to sit? Carb or Injected?
These fuel additives help prevent gas from going stale. In 4-6 months the hydrocarbons slowly oxygenate to form gum deposits which wreaks havoc on the fuel system, especially carbs.
A different problem is the ethanol in the gas which will combine with moisture in the air and separate out into an orifice plugging goo in 4-6 WEEKS, a totally different process. I don't think there is an additive that can stop that process (though the sellers of the additives claim otherwise).
Depending on how long you are out of commission I think you have three choices;
- Run the system dry and pull the tank, rinse it with kerosene, let dry and store it indoors where it won't rust.
- Fill it up with non-ethanol gas and add seafoam or whatever to stablize the gas to prevent formation of gum deposits.
- Fill it with normal gas, add stabilizer and run it to get into the carbs then top off the tank all the way to the rim (to prevent rust and minimize contact with the air) and hope for the best.