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The 3 Elements of Fuel Contamination

Posted by: Erik Bjornstad

Fuel that is clean and free from contaminants may be expected to give a long and useful service life. But sometimes things make their way into storage tanks that aren't supposed to be there and fuel contamination occurs.

fuel contaminationWater

It could be safe to say that nobody is ever going to keep water 100% out of a storage tank. Even in the best sealed tanks, water will collect simply through temperature changes and condensation on the tank walls. So we list water as a contaminant because it’s not supposed to be there, but it’s hard to keep it out.  It’s an especially big problem in little-used tanks where the fuel is rarely ever checked.

Water is a problem because it accelerates fuel instability and gives microbes a foothold for growth in the tank. 


A storage tank is the perfect environment for microbes to create a homestead. You get some of the water mentioned above, add microbes coming in through the air or even transmitted via fuel-drop from another source, and it doesn’t take long for the entire tank to become a breeding ground.  Especially with today’s ultra-low sulfur diesel fuels that don’t resists microbes like they used to.

Making sure you keep water under control is a key element to preventing this contamination. It’s also important to stay on top of tank housekeeping, being sure to fix any damaged seals or gaskets or caps that may other let in things from the outside that you don’t want in your tank.

Sludge and Out of Spec Fuel

Every so often, one of our fuel distributor customers will call us talking about a fuel problem they can’t quite wrap their heads around. They took a fuel sample before or after a fuel drop and there’s either an unknown sludge-like contaminant or they may even think someone has mixed in gasoline with their diesel fuel.

If you suspect that you have gasoline contamination in your diesel tank, the only way to know for sure is to submit a fuel sample for testing. They would test the density and the distillation curve to make the fuel’s combustion properties weren’t completely skewed.

Other posts on Fuel Contamination:

Storing Diesel and Biodiesel Cheatsheet Bundle

Buy the Ultimate Diesel Tank Cleaning Bundle

This post was published on September 29, 2015 and was updated on October 19, 2020.

Topics: Fuel Storage