Here’s what the big oil companies say:
From BP: As diesel gets older a fine sediment and gum forms in the diesel brought about by the reaction of diesel components with oxygen from the air. The fine sediment and gum will block fuel filters, leading to fuel starvation and the engine stopping. Frequent filter changes are then required to keep the engine going. The gums and sediments do not burn in the engine very well and can lead to carbon and soot deposits on injectors and other combustion surfaces.
From Exxon Mobil: If you keep it clean, cool and dry, diesel fuel can be stored 6 months to 1 year without significant quality degradation. Storage for longer periods can be accomplished through use of periodic filtrations and addition of fuel stabilizers and biocides.
From Shell: Typical issues are a result of water bottoms accumulating over a period of time in the storage tank that can lead to filter plugging and equipment corrosion along with a large amount of tank bottom material, which is mostly rust and scale… Since Ultra Low Sulfur Diesel (ULSD <15 ppm sulfur) was introduced to retail in the US in summer and fall of 2006, the diesel fuel industry has identified an increase of water in diesel fuel storage tanks contributing to an increase in the presence of microbial growth in fuel storage tanks in some cases and an increase in the number of product incidents with consumers. The entire industry has noticed this incrase. The filter can only handle a certain amount of sediments and only for a certain period of time. The key indicator is slow product flow due to clogged filters. If not timely addressed, this can potentially lead to water and tank bottom.
What special precautions need to be taken with diesel fuel that must be stored for a long period of time?
While storage stability should not be a concern for the majority of diesel fuel users, those who store diesel fuel for a prolonged period, i.e., oney ear or longer, can take steps to maintain fuel integurty. The steps below provide increasing levels of protection.