To keep your fuel system free of external debris, it has a number of protections. Your vehicle’s fuel tank has a locking cap. Fuel from your tank passes through filters before it reaches your engine. If contaminants are not typically getting in, how does a fuel system get dirty? The answer is actually in the chemistry of gasoline and the byproducts of the combustion process.

Gasoline is not just one compound. It is a complex mixture. Gasoline is formulated and mixed uniquely to areas of the country, time of year, and even down to specific station chains that may use proprietary additives. The goal is to provide gasoline that combusts as you expect consistently throughout the year, and helps meet regional emission regulations.

But all gas degrades over time and the formulation of gasoline pre-determines how long it will last. Some blends are expected to last up to six months, others just a few weeks. The biggest impacts to gasoline degradation speed are heat cycling, moisture, and exposure to oxygen. The impacts vary based on the formulation — it is unfortunately not as simple as winter and summer fuel. Summer fuel in dense areas can go bad faster than some winter blends due to oxygenators in the mix to reduce emissions.

How does this affect you as the customer? When gasoline interacts with oxygen, the result of the chemical reaction is sticky varnish deposits that can build up over time, clogging fuel passageways. This becomes more prevalent when vehicles are unused for periods of time, or if the gas itself is too old. Carbon deposits, a byproduct of the internal combustion process, can also build on critical components, such as fuel injectors, causing poor performance.