For over a decade, the EPA’s diesel fuel standards have required that ultra-low sulfur diesel (ULSD) be used in all on-road and off-road settings. This mandate was phased in over several years, starting in 2006 for on-road/highway diesel and continuing throughout 2010 to 2014 for off-road, locomotive, and marine diesel. Although ULSD is today’s fuel industry standard, many may not be aware of how it differs from earlier diesel fuels that contained more sulfur.
What Is the Difference Between Ultra-Low Sulfur Diesel vs. Normal Diesel?
Ultra-low sulfur diesel (ULSD) is a type of diesel fuel that contains a maximum of 15 parts per million (ppm) sulfur. In comparison, “normal diesel” or low sulfur diesel (LSD) contains up to 550 ppm sulfur. Prior to 1993 when the EPA began regulating sulfur in diesel, traditional diesel fuel contained as many as 5,000 parts per million (ppm) sulfur, making its sulfur content significantly higher than the diesel used today or even 20 years ago.
ULSD has a substantially different fuel chemistry compared to the higher-sulfur diesel fuels of the past. To optimize the production of ultra-low sulfur diesel from crude oil, refiners use a process called catalytic cracking which exposes the fuel to increased amounts of heat and pressure. Additionally, removing sulfur by hydro-desulfurization adds even more intense heat and pressure which stresses the fuel further. This results in an ultra-low sulfur fuel that is chemically active, unstable, and dynamic, causing it to require extra attention and monitoring.
What Are the Benefits & Drawbacks of Using ULSD?
Compared to traditional higher-sulfur diesel fuels, ULSD is cleaner-burning and produces fewer emissions, making it more environmentally friendly overall. However, these benefits also come with some unprecedented negative properties not found in earlier diesel variations. These include:
- Greater affinity for moisture
- Lower BTU value (negligible: 1% to 2%)
- Lower lubricity
- Less conductive
- Reduced resistance to microbial growth
- More corrosive
Since it was introduced, ULSD has been causing companies many ongoing issues due to its unique drawbacks. Corrosion from water contamination is a big problem for fuel storage vessels, metal fuel dispensing components, and fuel metering systems. The risk of filter plugging is increased due to the fallout of particulates from the fuel and the buildup of sediments. Water also provides a better habitat for microorganisms, and without higher levels of sulfur which used to act as a natural microbe inhibitor, fuel tanks are much more susceptible to bacterial and fungal overgrowth.
Luckily, fuel additives help compensate for many of ULSD’s negative qualities, making usage and storage much more manageable.
What Happens If You Don’t Use ULSD?
If you don’t use ultra-low sulfur diesel in an engine designed for it, it can lead to several issues such as mechanical malfunctions, environmental harm, legal problems, and higher maintenance costs.
- Engine Damage: Modern diesel engines and their emission control systems (like diesel particulate filters and catalytic converters) are designed to work with ULSD. Using higher sulfur diesel can cause these systems to clog or fail, leading to costly repairs.
- Increased Emissions: Higher sulfur content in diesel fuel leads to increased emissions of sulfur oxides, which contribute to air pollution and acid rain.
- Legal Issues: In the U.S., using non-ULSD fuel in vehicles that require ULSD is illegal and can result in fines or penalties.
- Warranty Void: Using the wrong type of diesel fuel can void the vehicle’s warranty.
- Reduced Fuel System Life: Sulfur in fuel can cause corrosion and damage to fuel injectors and pumps designed for ULSD.
How Long Does Ultra-Low Sulfur Diesel Last?
With proper storage and additive treatment, ULSD can last up to 18 to 24 months. If left untreated or in poor conditions such as high-humidity areas, it may degrade in just 6 to 12 months. Traditional higher-sulfur diesel doesn’t require additives to retain its integrity and has an average untreated shelf life of 12 to 18 months.
How to Prevent Common ULSD Storage Issues
The days of storing and ignoring diesel fuel are long gone. Today, industry leaders universally recommend preventive maintenance practices for ULSD fuel storage. Here are a few easy ways you can fight common problems, prevent shutdowns, and protect your equipment.
- Fuel Condition Monitoring: Regularly monitor your fuel’s condition and remove any water that is present in storage tanks.
- Fuel Testing: Send fuel samples to a fuel testing laboratory as a matter of routine to test for stability, water, particulate, microbial life, and organic/inorganic contamination.
- Fuel Additives: Use fuel soluble additives that include film-forming corrosion inhibitors, dual phase antimicrobials, demulsifies, and organic dispersants. Proper additive application improves fuel storage stability, prevents corrosion, kills and prevents microbe growth, disperses sediment, and manages moisture accumulation.
- Fuel Filtering & Tank Cleaning: Filter your fuel and clean/polish your tanks when needed.
If you follow these steps, you’ll be able to reap the benefits of ULSD while minimizing its downsides. To learn more about our ultra-low sulfur diesel services—including diesel delivery, fuel tank rentals, and fuel polishing—contact a member of our team today!