The transition to ultra-low sulfur diesel (ULSD) has created the need for additives to replace the lubricating properties of sulfur-based compounds. Typically, surfactant-based fuel additives with good fuel solubility are used to bring fuels to accepted lubricity levels. These additives bind to a wide range of surfaces including metal (lubricity and corrosion protection), water (emulsifier), fuel wax crystals (anti-settling agents), and injector deposits (deposit control modifiers).
Since there are no currently adopted industry standards addressing the use of fuel additives, it is not surprising that problems arise when they are blended improperly, or incompatible fuel additives are mixed together in the fuel. One of the most well-known fuel chemistry problems is the reaction of acids and bases contained in lubricity and corrosion inhibitor additives. Carboxylic acid-based surfactant additives can react to form metal carboxylates. While the acidic surfactant is soluble in ULSD, the metal carboxylates are insoluble and tend to form contaminants that are often smaller than 4 microns in size. These particles can lead to premature plugging of fuel filters, and if the filters used are not efficient enough, they can travel through the filter and be sent to the fuel injection system. Once in the high-pressure common rail (HPCR), metal carboxylates are known to cause internal diesel injector deposits that prematurely damage injectors.
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Ensuring that the fuel is clean and dry, and knowing which additives were added where/how to the fuel can make a difference. End-users sometimes use additional additives with the misconception that more is better; when the total additive dose becomes too high, soft contaminants can quickly and prematurely plug filters, reducing the expected service interval.
Watch Your Biodiesel Blends
Another example of a potential contaminant is glycerin from biodiesel blends. While there are specifications in place for total glycerin, the exact blend percentage, temperature and water content can all affect how much glycerin a fuel can hold in solution. Once it precipitates, or comes out of solution, it can negatively impact filterability in ways similar to excess additives, drastically reducing expected filter life. Biodiesel with lower free glycerin levels, and better storage practices of keeping the fuel dry and protecting it from extreme temperature swings, can help mitigate this issue.
Generally, replacing a filter with a less efficient one is not advisable. Fuel filters on modern engines are protecting sensitive downstream components, and using a less efficient filter than the intended level of protection can result in premature wear and potential engine failure. What is more important is understanding why your filters are plugging, and from where the contaminant originates.
A reputable filtration supplier can help investigate the root cause and advise proper corrective actions to eliminate the problem without sacrificing protection. Proven media technologies like Synteq XP™ used in Donaldson Blue® fuel filters will deliver the highest levels of efficiency and contaminant retention under dynamic conditions.
