Fuel stabilizer works by slowing the oxidation process of gasoline. It helps keep heavier compounds in solution and allows the fuel to absorb some of the moisture that forms in a tank instead of separating into layers. Most fuel stabilizers protect fuel for 12 to 15 months.
During normal operation, a car has little need for a fuel stabilizer. The driver fills the fuel tank and drives the car to consume the gasoline before it has a chance to separate. However, when the vehicle is stored for an extended time, gasoline has time for volatile compounds to evaporate and the fuel to separate. The next time the owner starts the engine, varnish plugs the fuel injectors or carburetor. The problem often affects seasonal vehicles, such as snowmobiles or boats, but it also affects automobiles in storage.
Storing a vehicle with stabilized fuel in the lines offers advantages over storing it with an empty fuel system. Dry storage often results in cracking of rubber connections and allows water to condense in the lines. For best protection, the owner adds the stabilizer to fresh gasoline in the tank and operates the vehicle a few minutes to ensure it consumes any unstable fuel before storage.