Ultra-Low Sulfur Diesel and Fuel Lubricity Concerns


Operators know maintaining proper lubrication of the fuel system is vital to lengthening the service life of their Big Rigs. Improper fuel system lubrication will lead to increased wear and eventual failure of fuel pumps, injectors, and other fuel distribution components. Current federal mandates require all highway diesel fuel to contain lower sulfur content than the previously available fuel. This newly required fuel blend, known as Ultra Low Sulfur Diesel (ULSD), is a result of government initiatives to reduce highway emissions and atmospheric pollutants.

Unfortunately, ULSD has disadvantages that can cause headaches for the heavy duty commercial trucking industry. A common approach to mitigating the problems caused by ULSD is to utilize diesel fuel additives. Although fuel additives increase operational costs initially, over the long-term, additives have demonstrated a substantial return on investment for many semi-truck drivers.

What is ULSD?

To become Ultra-Low Sulfur Diesel, standard diesel fuel must undergo additional processing, known as hydro-treating. This process strips Sulfur and other compounds from the fuel – which results in a fuel that when burned releases fewer airborne contaminates. Unfortunately, the hydro-treating process strips away many of the lubricating compounds in the fuel- leaving many diesel components susceptible to damage. The law requires all Big Rigs and highway diesel vehicles to use ULSD. Additionally, the hydro-treating process removes some of the power density from the fuel, you can anticipate slightly lower performance and efficiency from the ULSD blend.

ULSD Disadvantages

Lubricity – The majority of Sulfur particles are removed from ULSD, the blend will contain 15 ppm (parts per million) of Sulfur or less. This results in a “dryer” fuel in which the lubrication properties are greatly reduced. This dry fuel combined with the demanding operating characteristics of fuel components results in increased wear, which ultimately raises maintenance and repair costs for the heavy duty commercial trucking industry. Lubrication is critically important for the fuel system components, considering a diesel fuel system can operate at a pressure of 30,000psi or greater. The fuel pump and fuel injectors are highly susceptible to damage due to inadequate system lubrication.

Higher Cost – In addition to the lower power density of ULSD, the cost for this blend is also higher. The hydro-treating process adds between 0.05 to 0.25 cents to the cost of one gallon of fuel. This is a significant cost increase that adversely impact the commercial trucking industry. For perspective, a typical big rig can hold nearly 400 gallons of diesel fuel, which results in a price hike of $100.00 per tank of fuel. Federal regulations often target the trucking industry, when realistically Big Rigs are quite efficient. Remember, with one gallon of fuel, a semi engine can haul 80,000 pounds for nearly seven miles. This is quite impressive, and a testament of the engineering and performance capabilities of modern 18-wheelers.

Ensuring Proper Fuel Lubricity

To replenish the lubricating properties of ULSD many Big Rig drivers utilize fuel additives, which are added directly to the fuel tank. These additives provide corrosion inhibitors, increased lubricity, detergents, and cold flow improvers. Ultimately, the goal is to extend the life of the engine and fuel system components by reducing wear and tear. It is common for refineries and individual fuel stations to add their proprietary blend of additives to the fuel they sell, which may reduce the need to purchase additional fuel additives. However, by relying on the fuel station to ensure the proper fuel blend, you are placing the health of your big rig into the competence of strangers. To reduce this liability, many operators choose to add their own fuel additives.

Advantages of Diesel Fuel Additives

Increased Lubricity – This is the most important feature of most diesel fuel additives. Many Big-Rig operators, hotshot drivers, and recreational diesel owners rely on these additives to preserve their trucking investments.

Anti-Gel – Cold environments with sustained temperatures below freezing can cause diesel fuel to gel. Gelling is when the fuel begins to separate into its base components, which will restrict fuel flow to your engine, most likely by clogging the fuel filters. Additives will reduce this separation temperature and ensure your fuel flows normally in cold temperatures.

Improved fuel efficiency – This is possibly the most contested feature of diesel fuel additives as many additives claim to improve your average MPG. However, these claims are reasonable considering most additives contain a cetane booster and reduce fuel system corrosion, which results in longer and more reliable engine operation.

Road Reports

A hotly contested debate on diesel additive superiority can be found on any 18-wheeler online forum. Opti-Lube, Power Service, and Lucas are some of the more popular brands, with Opti-Lube being one of the highest priced options. Regardless of the debate regarding brand name, the consensus among Big-Rig truckers is that diesel fuel additives do reduce wear on fuel system components. Some drivers who utilize additives report driving over 500,000 miles on the original set of fuel injectors.


Diesel fuel additives address the need for greater lubrication properties that ULSD fuel does not provide. Although additives can be expensive, they provide operates with the assurance that Big-Rig will continue to provide long-term reliable service. An 18-wheeler is a significant investment that can be expected to operate for over 1 million miles, it may be prudent to invest in a diesel fuel additive to ensure your truck reaches this milestone without major issues.