why is filling the tank a good idea, especially when it won't be driven for several months? I would just keep a little bit of gas with an additive.

 

You want to completely fill the tank to prevent moisture build up inside the tank which will eventually end up with having water in your fuel. The less space inside the tank the less moisture build up and thus the less water in the fuel. With a full tank you won’t have to worry about any problems.

Also a full tank is safer then an empty or less full tank. Less fuel in the tank means more room for fuel vapors to develop…