With winter storage season comes the frequently-asked question, “What’s the best way to winterize my gasoline tanks?” Our best answer comes from an understanding that there are three basic threats to your gasoline fuel system during long-term storage.
1) “Bad Gas.” When left sitting still, gasoline can begin to “go bad” in a matter of months. Left untreated, some of the fuel components begin to oxidize and form a gum-like substance. This is sometimes known as “going stale,” or “varnishing.” The substance settles in fuel lines and tanks, carburetors and injectors. When you try to burn this fuel, deposits can form in the combustion chamber. Over time, these deposits build up and reduce your engine’s performance.
The good news is that there are a variety of gasoline treatments, or stabilizers which are effective in slowing this breakdown and prolonging the life of your gasoline for a usual winter storage period. Make sure to read the label to ensure that your stabilizer does not contain alcohol, because ….
2) “E10.” In most states, all gasoline sold contains ethanol. E10 gasoline contains 10% ethanol alcohol, and this ethanol can create havoc with your fuel system. It often “eats” or degrades the insides of fuel hoses and lines, causing particles of rubber and plastic to clog injects and carburator jets. Ethanol also loves to mix with water. Get more than 500 parts per million water in the fuel and it bonds with the ethanol and then plops to the bottom of the tank in a powerless blob. That’s phase separation, and it takes the octane with it. If this crud burns through the engine, it abrades injectors, nullifies the work of lubricants and may cause catastrophic damage.
It happens suddenly, and adding stabilizer can help retard the process. But once it happens, contrary to statements made by some companies that produce fuel additives, there are no additives that can make stale or phase-separated gasoline usable.
The real enemy here is water. Our fuel tanks are vented to the outside air, and that air contains moisture which can condense on the walls of fuel tanks. E10 can hold up to half of one percent of water by volume, and the water molecules will dissolve in the fuel. The best way to prevent water from ruining your gasoline is to top off your tank before putting your boat away. This will decrease the volume of air space so the tank can’t “breathe in” as much damaging moist air, and leaves less space on tank walls for condensation to form.
3) “Fire.” Another reason to leave your tanks full for the winter is to reduce the amount of space in the tank for gasoline vapor to collect. Gasoline doesn’t burn in liquid form. It’s the gasoline vapor that can ignite and create a catastrophic fire aboard your stored boat. Minimizing the air space in the tank also decreases the space available for vapors to collect.
So fill your tank to keep your gas dry, add alcohol-free stabilizer, and put your boat to bed for the winter knowing that it should start and run well in the spring.