As far as winterizing a Jet Ski / Wave Runner or Sea-Doo, it's best now to add Sta-bil to the gas and top the tank off for the winter. This will keep most of the moisture out of the tank, since there is very little room in the tank to attract the moisture. An empty or almost empty tank is more susceptible to getting moisture in it, cause it's not full letting the gas take up the room in the tank. This new change was told to me by a very reliable source, who I trust very much on keeping my toys mechanically sound for my use.