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Fueling fleet operational efficiency: Proper diesel storage

Oct. 22, 2018
The value gained from investing in regular fuel storage maintenance should not be overlooked.

Better fuel quality means fleets run more efficiently, which in turn helps a fleet owner’s business run smoothly. However, fuel can be easily contaminated if not stored correctly. So, why isn’t there more emphasis placed on proper diesel fuel storage?

It can be hard to visualize the connection between how diesel fuel is stored and the effects it has on quality and performance in a fleet. That said, the value gained from investing in regular fuel storage maintenance should not be overlooked.

The average U.S. fleet spends between 30 and 40 percent of its maintenance, repair and operations (MRO) budget on fuel, according to an analysis by the American Transportation Research Institute (ATRI). Yet fuel quality or storage was not listed among the concerns in ATRI's annual Top 10 Critical Issues in the Trucking Industry report in 2017. Every individual step in the supply chain matters, and proper diesel fuel storage is critical to the performance of a fleet. Otherwise, the fuel supply may fall victim to a variety of common storage problems such as water and particulates, ultimately affecting fleet performance and efficiency.

But before exploring common storage problems further, fleet owners should note the difference between regular diesel and biodiesel fuel.

Regular diesel vs. biodiesel

Understanding the difference between regular diesel versus biodiesel fuel and the implications this holds for fleets is the first step in proper diesel storage.

Biodiesel contains oxygen molecules that cause it to be more susceptible to oxidation. Therefore, fuels that have any bio-content should only be stored up to six months, while regular diesel without bio-content can be stored longer. It should also be noted that there can be up to 5 percent of bio-content in any final diesel fuel product, without requiring it to be labeled as such. Fleet owners should confirm the amount of bio-content in their diesel fuel with their supplier. Ultimately, the presence or absence of bio-content in the fuel supply should be kept in mind when evaluating its lifespan.

No matter the lifespan difference between regular diesel and biodiesel fuel, fleet owners risk the occurrence of two common storage problems – water and particulates – when the fuel is not stored properly.

Common Storage Problem No. 1: Water

The presence of water in tanks is the most common on-site storage issue. Given most diesel fuel storage tanks are outdoors and vented to the atmosphere, daily temperature highs and lows can cause condensation that impacts water levels in the fuel tank. Another factor that may affect water levels is how the product is manufactured and transported. The presence of water in diesel fuel is ultimately inevitable. However, there are best practices to help ensure water contamination is at a minimum.

Tanks should be checked for the presence of water every week, using a water finding paste that detects water levels. It is suggested that water levels should be no more than three inches in any bulk storage tank. To keep water levels at a minimum, regular water removal is recommended. Storage tanks should also be kept as full as possible; less air in tanks minimizes water condensation and slows fuel oxidation. Fleet operators must examine the appearance of the stored supply as well. If the fuel appears hazy, there may be excess water in the tank.

Keeping water levels to a minimum is critical in preventing microbial growth, especially in humid climates. Microbes thrive in the presence of water, resulting in the generation of slimes, molds and other bacterial growth that can coat surfaces and plug filters. This is especially important for fuels containing bio-content, which are more susceptible to microbial growth, according to the U.S. Department of Energy's Biodiesel Handling and Use Guide.

Common Storage Problem No. 2: Particulates

Another common storage problem is particulates. Diesel fuel touches various metal surfaces throughout its supply chain. Over time, these surfaces can degrade and cause particulates such as rust or debris to mix with the fuel. The fuel itself also oxidizes and can generate particulate matter. 

Filters are necessary to ensure these particulates do not pass through from the tank to its final destination. Therefore, filters in your dispenser pumps and in your fleet should be checked at regular intervals to prevent premature filter plugging, which may be a sign that your fuel is compromised and that you’re at risk of contaminated fuel entering your engine. Consider replacing the fuel filters in your fleet every oil drain interval to ensure optimal operations.

Additionally, when fuel is taken out of service station tanks, the off-take point should be three inches from the bottom of the tank to avoid the possibility of dispensing water and particulates, which will be at the bottom of the tank if present. For above ground bulk storage tanks, consider having the floor and at least the first three feet of the internal wall lined with epoxy, which provides corrosion protection and sealing, as suggested by API 652 specification.

To prevent contamination, fleets must proactively maintain their fuel storage tanks to ensure the quality of their diesel fuel and optimized operation of their fleets. Fleets should have a comprehensive maintenance program in place that includes maintaining filters and adding an epoxy lining as two key measures. Should contaminated fuel ever reach fleet engines, the chances of engine issues like rough idling, poor running or even engine damage will increase.

On top of maintaining proper diesel storage practices to hinder the prevalence of water and particulates, fleet owners should be mindful of regulations that could impact diesel storage.


While there are no federal regulations regarding fuel storage units, policies may vary from state to state or from county to county. Therefore, it’s important to familiarize yourself with the local statutes where your tank is located.

Over the years, several industry organizations have also published recommended best practices that some fuel handlers have used as guiding principles. The API, ASTM International and Coordinating Research Council (CRC) have all published reports and guidelines that serve as the basis of many current diesel fuel storage practices.

Beyond regulations, fleet owners should also keep a pulse on auto industry trends.


As it stands, diesel fuel storage isn’t always top of mind for fleet owners. However, they will begin to recognize the importance of this practice as the auto industry evolves.

As vehicle emission requirements become stricter and vehicle durability grows in importance, fuel quality is becoming a greater area of focus. It is anticipated that the industry will start to see a growing voice among OEMs to promote industry-wide practices to ensure fuel quality.

An increasing prevalence of above ground storage tanks in the U.S. is also likely. While the trend has been gaining traction in other parts of the world in recent years due to updated regulations, fuel handlers in the U.S. have been slower to adopt, largely due to the higher cost. However, many are realizing the benefits such as better visibility and ability to drain excess water.

Overall, fleets should work closely with their diesel fuel supplier to devise a best-in-class maintenance strategy and mitigate degradation across the equipment lifecycle. Freight demands and the continued growth in the transport of goods has never created a better need for proper diesel fuel storage. In fact, ExxonMobil’s 2017 Outlook for Energy: A View to 2040 expects diesel use will continue to rise globally by approximately 30 percent through 2040, mainly to meet increasing trucking demands. Therefore, fleets need to make their dollars go further and keep trucks on the road by ensuring their diesel fuel supply is properly stored, to optimize operational effectiveness.  

This Fleet Maintenance online exclusive was provided by ExxonMobil's Global Commercial Fuels Marketing Manager Kurt Ilgenfritz.


June 25, 2007