You can also use a product called Star Tron by Star Brite. It is a enyzme that counteracts the effects that ethanol-based gas creates.
Way better than Sta-Bil. In fact, I've used it to restore stale gas. I was amazed how well it worked.
Here is the link to the company. I am in no way associated with them, just use the product and know a bunch of others who do as well.
http://mystarbrite.com/startron/