I cannot empahsize this enough... if your car is going to sit in excess of a couple of months, put stabilizer in the tank BEFORE it goes into storage. Several different brands are available, I've always used Stabil and never had a problem. The thing with gas sitting for an extended amount of time is that all the particulates in the gas settle down to the bottom and the gas begins to seperate into different layers. Upon start-up months down the line, the octane, cleaners, particulates, and everything else about the gas is just simply put, way off. Before it goes into storage, fill the tank up to a decent level, (3/4 full is usually good), add stabilizer and drive the car for several miles to mix the stabilizer into the gas tank. Your car is now ready to sit as long as you can do without it.

-Flup