The typical conditions of summer work together to decrease the effective storage life of diesel fuel. That’s especially true with ultra-low sulfur diesel.
Back in the day, you could store diesel fuel and expect to get multiple years of quality storage life out of it. Google U.S. Army fuel specifications and you can find references from the 1980s and 70s that talk about this.
This brings into play the need to treat stored diesel with diesel stabilizers to protect its quality and ensure that it remains useable when you need it at some point in the future.
If you think about it, there are 4-5 factors that influence petroleum storage life. At least 4 of these are amplified in the summer time.
Fuel sitting in storage tanks doesn’t have to worry about light exposure. Heat is a completely different matter. Fuel stability has everything to do with the chemical reactions happening within the fuel. All diesel fuel (and gasoline, for that matter) has unstable molecules present that seek to react with other molecules in the fuel. This starts a chain reaction that eventually results in the fuel darkening and the formation of sludge, varnish and asphaltene deposits.
Heat and light accelerate this process simply by providing more energy for these reactions to feed off. We learned in high school chemistry that most reactions happen faster when things are hot than when they are cold. That’s because most chemical reactions require some kind of energy input to make them happen. The more heat present, like with hot summer weather, the more energy is available for more reactions to take place to cause stored diesel fuel to lose its quality and become unstable.
Treating diesel fuel in the summer time enables it to withstand the summer heat by stopping these reactions from happening.
Water wrecks stored fuel quality in a couple of ways. Water itself contributes to hydrolysis reactions that speed up stored fuel decomposition.
Hot summer weather speeds up water collection in storage tanks because of greater condensation at night. The air in the storage tank stays hot during the day, keeping all that water vapor dissolved. It cools down at night, and the water vapor condenses on the inside surfaces of the tank, eventually forming a water layer at the bottom of the tank.
Oh, and the presence of water is essential for microbes to be able to grow.
And speaking of those……fuel microbes grow faster in the summer because microbes like to grow in hot conditions. Microbes can really a number on fuel stability because of the acids and biological substances they excrete that contribute to these chemical reactions in the fuel.
Better yet, couple your diesel stabilizer with a fuel biocide. A good diesel stabilizer is important to use in summer fuel storage for exactly the reasons given above. Instability chemical reactions happen a lot faster in the summer. A fuel stabilizer will cancel these reactions out and enable the fuel to be stored through the summer without any worries about its quality. And a good biocide treatment in the fuel will kill fuel microbes before they have a chance to establish themselves and form problematic infestations.