I have heard this stuff used 2 ways. One, like mattman, where it is put in every tank of gas. The other, where you really dose the gas with it. Then, you go through a series of certain running techniques. This way, it is basically an enema for your engine. This is especially important to clean the carbon out of your engine, especially if you idle a lot, where the carbon will build up. This second method is known as a decarb.