(This article was written by Olivia Madiraca, Sunoco’s Manager of Race Fuels Development and Technical Support. Sunoco is the official fuel of the SCCA®.)
As winter approaches, car enthusiasts need to consider how to prepare their car for the off-season. One of the most important aspects of winter storage is properly readying the car’s fuel system for months of sitting stagnant. Many cars are stored outside at ambient temperatures and conditions, meaning they’re exposed to temperature changes, humidity, and moisture from rain and snow. As the gasoline sits in your car over winter, it will begin to degrade and age, the results of which are only exacerbated by the outdoor conditions. It’s also important to note that oxygenated fuels, such as fuels with ethanol, in a car for extended periods of time could lead to damage of gaskets and hoses in the fuel system.
If you just read that and thought: My competition vehicle is stored in the garage or trailer, so this is not my concern. We ask you: Is your tow vehicle treated as kindly? And even if your competition vehicle is under cover, it’s likely still experiencing temperature swings.
As a vehicle sits exposed to ambient conditions for an extended amount of time, several things happen to the fuel. The fuel will begin to degrade and oxidize; oxidation leads to gums and varnish formation and lowers the octane of the fuel. Gums and varnish will cause fouling and deposits in an engine, which upon starting in the spring, will lead to poorer engine performance. The aromatic molecules that make up gasoline have a lower octane number after oxidation; these aromatic molecules have the largest octane rating of all the components of gasoline, so their oxidation can have a big impact on octane
The fuel will also undergo some evaporation. Even at low, winter temperatures, the light end molecules like butane in gasoline will evaporate. Without light ends, the fuel will be much heavier and will make the engine difficult to start, as they are what allow the fuel to burn at lower temperatures.
If a car has an ethanol-containing fuel in the system, the fuel will absorb moisture and water from the atmosphere. Ethanol is hygroscopic, meaning it will readily absorb moisture from the environment. It’s no surprise to anyone who’s familiar with cars that moisture and water in gasoline will cause significant issues. High moisture content or bulk water in a fuel system can cause poor performance and corrosion. Ethanol can also degrade rubber parts in the fuel system due to its corrosive nature.
All of these potential issues make it clear how important it is to properly prepare a car for over-winter storage. Two options for storing a car are to empty the fuel system or to select a fuel compatible with storage.
Emptying a fuel system can be difficult and exposes the system to more air, which means more risk of corrosion and issues. It also comes with the chore of safely disposing of the fuel, which can be difficult in cars that use leaded fuels. Selecting a safe fuel is often the better option for storage.
Sunoco offers two great fuels for storage; one for any application and one for cars that use leaded fuel only. Sunoco Optima is a great choice for long-term storage of any vehicle. It’s a 95 octane, unleaded, unoxygenated fuel that contains a robust additive package (antioxidants, detergents, and corrosion inhibitors), all of which makes Optima an exceptionally stable fuel. Studies have shown even after three years, the fuel’s properties remain the same. Sunoco Surge is a leaded fuel that, like Optima, contains no ethanol and has additives that make it an excellent candidate for storage. Its shelf life is in excess of two years. The long shelf lives, lack of oxygenates, and additives make Optima and Surge our recommended fuels for over winter storage.
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As winter sets in, don’t chance unnecessarily damaging your competition vehicle or tow vehicle as they sit unused – an ounce of prevention now will set you on the path for success in the coming year when it’s time to get out there and have #funwithcars.
Photo by Erik Mclean
