Fuel Additives Address Diesel Deficiencies - Engine Builder Magazine

Fuel Additives Address Diesel Deficiencies

Advancements in diesel fuel additives continue to play a pivotal role in improving the performance and efficiency of diesel engines.

Diesel fuel is a perfectly imperfect product. Yes, there is the industry standard specification ASTM D975 that outlines minimum performance requirements. But, this mostly confirms that refiner A in the Gulf Coast produces diesel fuel with the same baseline characteristics as refiner B in the Midwest.

Gasoline, on the other hand, has to meet a Federal Lowest Additive Content, or LAC, mandate that ensures every grade includes a certain amount of detergent and satisfies all gas engine-related emissions requirements. That also helps keep fuel injectors clean and catalytic converters in working order.     

AMSOIL additives

“The ASTM D975 does a reasonable job of making sure the fuel won’t tear up your diesel engine,” says Dr. Ray Burns of Lucas Oil Products, “but it doesn’t do anything to really elevate the fuel’s performance. It’s basically just a minimum standard, so it’s important to consider where you’re getting your fuel from and to supplement it or boost its performance should your application dictate it.”

Fortunately, aftermarket additives are constantly being formulated and refined to not only boost the performance of diesel fuel, but also protect and extend the lifespan of fuel system components, prevent deposit buildup and combat a host of other unwanted hazards resulting from untreated fuel. Let’s take a closer look at how some key additives are designed to address specific – and emerging – challenges and enhance various aspects of diesel fuel and engine systems.     

Cetane Improvers

These additives improve the cetane number of diesel fuel, which measures its ignition quality. Basically, cetane extends the burn of the fuel in that it enables a more complete burn of the fuel molecule. Higher cetane numbers mean more efficient combustion.

“Now, you’re using all that fuel to make power,” explains Kyle Fischer of Hot Shot’s Secret. “By contrast, lower-cetane fuel means more fuel is getting passed off to the diesel particulate filter (DPF) and the exhaust side… a full burn means you’re using less fuel, so you’re maximizing the fuel that’s in the tank. That’s where your mileage and power comes from.” 

In high-rpm or racing applications especially, higher cetane levels absolutely “help deliver additional horsepower to the engine by changing that combustion dynamic and changing the combustion timing,” Burns says. “It changes the amount of power, or the rate of power release from the fuel that you’re combusting, and that can deliver improvements in performance.”  

During the refining process, diesel fuel tends to lose its cetane properties. And, while studies show diesel engines run best at levels between 45-50, the ASTM D975 standard sets the minimum cetane number at 40. Most diesel pumps hover at or just above that figure.

Hot Shot's Secret additives

Fischer points out that while it helps improve the fuel’s combustion efficiency, raising cetane levels by seven points with a Hot Shot’s Secret additive was found to also reduce the emissions entering DPF systems by up to 50%. 

“That alone doubles the life of your DPF,” Fischer says, citing recent EPA testing in conjunction with the city of Columbus, OH. “You’re sending half as much particulate to it. A lot of people don’t equate cetane to preventative maintenance, but it absolutely is, because it takes a lot of wear off that exhaust system.”   

Lubricity Improvers

Diesel fuel itself lacks adequate lubricity, which in turn leads to increased wear and tear on fuel system components like pumps and injectors. Lubricity improvers help reduce friction and wear while extending the lifespan of critical parts.

This was less of a concern prior to the early 1990s, when diesel fuel contained up to 5,000 ppm of sulfur. But, in 1993, the EPA decided to drastically reduce that sulfur content, and in doing so, they removed elements that helped lubricate the fuel. Nonetheless, a 99% reduction in sulfur levels was phased in, followed by another 99% reduction of all remaining sulfur in 2006. Today’s ultra-low sulfur diesel fuel contains just 15 ppm of sulfur, and it’s had a notable effect on lubricity.

To illustrate the importance of proper lubrication, Mark Nyholm of Amsoil points to common rail diesel injectors, which “open and close five to seven times per combustion cycle. That pintle opens and closes and hammers its seat five to seven times very quickly. The lubricity of the fuel helps cushion the blow of that pintle closing, and ensures you don’t have premature wear to your seat or your pintle. 

“If you do [have wear], you’re stuck with a worn surface or irregular surface in which it doesn’t seal, and then it leaks fuel at the wrong time. Lubricity is very important to be used on an every-tank basis to protect the injectors, as well as the pump, from premature wear.”

Arguably the poster child for lubricity issues, Bosch’s troubled CP4 high-pressure fuel injection pump is now the subject of multiple class-action lawsuits stemming from abnormally high failure rates. A design flaw that sent metal and debris down the fuel lines, into the injectors, and then back up through the fuel system was a core problem. Just as damaging, Fischer says, is that the CP4 was made for higher-lubricity European fuels as opposed to the much drier American diesel. How do we know? Because CP4s in identical vehicles tested off the assembly lines had significantly higher failure rates in the U.S. (upwards of 8-9%) than in Europe (less than 1%). The only difference, he notes, was fuel type.   

“A lack of lubricity [in those CP4 pumps] is causing premature wear, and as soon as it starts to scuff, that metal goes everywhere and it’s game over,” Fischer says. “Lubricity is the number one thing. I tell everyone, ‘If you don’t believe anything I say, and you don’t believe any of the science or data I show you, at the bare minimum, please add lubricity to your fuel.’ To me, it’s mandatory to protect the system.”

Cold Flow Improvers (aka Anti-gel Agents)

In colder climates, diesel fuel can thicken and become more viscous, making it difficult for the engine to draw in and atomize the fuel properly. Cold flow improvers, or anti-gel agents, are designed to prevent wax in the fuel from solidifying, which can clog fuel lines and filters. These additives work by lowering the fuel’s cold filter plugging point (CFPP), or the point at which it begins to thicken and form wax crystals. Reducing the CFPP allows the fuel to flow freely through the filter, even in extremely cold temperatures.

Burns likes to use the analogy of a comb when describing how some anti-gel agents disrupt the waxy buildup that forms within diesel molecules. “These molecules tend to be a long, straight chain,” he says. “We call them paraffins, but they look waxy. A cold flow improver is like a comb that gets between those waxes and prevents them from crystallizing together and forming a big gel. 

“There’s also one called a Wax Anti-Settling Additive (WASA),” he continues, “which is another type of additive that disrupts the wax crystallization. It also helps to keep those small wax particles that can form dispersed in the fuel, so they don’t settle together in a crystallizing gel.”     

These additives are especially important as climates become increasingly unpredictable. Here’s why: Refineries blend their fuels based on seasonal averages, and their data comes from tracking recorded temperatures from year to year. 

Lucas Oil additives

“The problem is, if you get a cold snap like Texas saw a couple of years ago, and everything freezes,” Nyholm says, “well, they weren’t protected because it wasn’t a seasonal average. It was an anomaly, and the fuel wasn’t capable of protecting their equipment, so everything froze.

“The refinery has you protected to a certain temperature,” he adds, “but eventually you’ll see swings in temperatures that’ll push that limit. That’s why you would use cold flow improvers, to proactively and preventatively ensure you’re not the guy stuck on the side of the road. They prevent the solidification of waxes, keeping them liquefied in solution so they don’t plug up your system.”     

Detergents (Injector Cleaners)

One of the main functions of diesel fuel additives is to prevent the buildup of deposits on fuel injectors. Over time, the high temperatures and pressures within the injector system can cause the fuel to break down, leading to the formation of carbon and other residues. These deposits can restrict fuel flow, reduce atomization, and ultimately prevent the injectors from working properly.

Detergents, or injector cleaners, help keep these critical fuel system components clean and unimpeded. “They’re going to provide a cleaning capability to your injectors, both internally on the pintle and on the nozzle,” Nyholm says. “It’s also going to provide cleanliness in the combustion chamber to improve the combustion efficiency. And, it’s going to help prevent carbon particles from agglomerating in the fuel tank, plugging your fuel filter. The detergents are really important on an every-tank basis, especially with today’s fuel.” 

One byproduct of modern diesel fuel handling and processing is the emergence of Internal Diesel Injector Deposits, or IDIDs. While not an entirely new phenomenon, this sticky, gooey substance that builds up inside the injector tips and bodies is now seen as a primary, and increasingly common, cause of injector problems.  

“What that [substance] does is it affects the spray pattern, so you’re not hitting that sweet spot of the piston,” Fischer explains. “The way diesel engines work…one of the most important parts of that is the injector itself, which atomizes the fuel. As soon as you start messing with that spray pattern, whether it’s coming out in glumps rather than spraying into micro-sized particles, or altering the effect of how it’s coming out of the injector and missing that sweet spot of the piston. These are all problems that cause fuel economy loss, power loss and other issues.”

Fischer stresses that while a number of additives are capable of removing carbon and other deposits, “it takes a specific kind of injector cleaner to clean out the IDIDs. They don’t clean easily. There’s an expensive, unique chemical that can do it, though, so it’s very important to have the right injector cleaner.” 

The Future of Additives

Advancements in diesel fuel additives continue to play a pivotal role in improving the performance and efficiency of diesel engines while protecting and extending the lifespan of fuel system components. Though not mentioned earlier, additives like rust and corrosion inhibitors, and fuel stabilizers to prevent oxidation during storage are also designed to help compensate for the shortcomings of today’s diesel fuel.

Looking ahead, our sources anticipate, among other developments, even more inclusion of biofuels as a means of addressing climate change on state, federal, and even global levels. Blending the fatty acids from plant-based oil, cooking oil, or unused restaurant grease together with petroleum-based diesel creates biodiesel, which has gained popularity across the U.S. and around the world as a more environmentally friendly, cleaner-burning fuel source. 

“There’s a lot of interest in sustainability, or trying to decarbonize the fuel industry as much as possible,” Burns says, “and inclusion of biofuels is one way to do that. In fact, in Europe there’s a newer type of fuel called HVO, or hydrotreated vegetable oil, that is a unique take on biodiesel. Basically, it’s treated with hydrogen in such a way that it goes from being an oxygen-containing molecule into a full hydrocarbon with no oxygen in it. They’re taking a plant-based oil and turning it into something that looks much more like petroleum-based oil, but without some of the issues that come from using cooking fats or fatty acid methyl esters in diesel.

“That’s becoming more commonplace in Europe,” he continues. “It’s not as common in the U.S., although it is available in some places, and it probably will continue to proliferate as the interest in sustainability and reducing the carbon footprint of the industry increases. That impacts additives as well because it’s all about balancing and selecting the additives you need to make sure the engine is well protected and that it’s going to perform the way you need it to and last for a long time.” EB

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