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How fuel additives can help diesel engines

Diesel engine vehicles generally run more efficiently than their gasoline engine counterparts, however the nature of diesel fuel could cause some drivability problems. Diesel fuel additives can help, but only as a short-term solution.

Water and dirt in diesel fuel

Diesel issues can begin even before the fuel gets pumped into your tank. Diesel fuel delivered to gas stations is not necessarily clean and free of containments. In a 2016 study, Donaldson Filtration Solutions found that a single delivery of 7,500 gallons of diesel fuel contained one to two gallons of water and a cup of dirt. Once delivered, even more water and contaminants can get added to the fuel due to poorly maintained storage tanks at fuel retailers.

Fortunately, diesel fuel systems have water separators to extract moisture and fuel filters to capture other contaminants, and both protect costly fuel injection components and help prevent problems. Critical maintenance steps for diesel engines are to periodically drain the water separator and replace the fuel filter.

Be aware of diesel engine drivability issues

Even if you keep up with proper maintenance and use high quality diesel fuel, your engine still could encounter drivability issues.

  • Microbial growth – If too much water accumulates in the fuel tank, it can “fall out” and settle to the bottom of the tank. When this occurs, bacteria and fungi in the fuel can multiply, forming a black goo that can plug fuel lines and filters.
  • Icing – Retained water in the fuel tank or water separator can freeze in winter, blocking fuel flow and keeping the vehicle from starting.
  • Fuel gelling – Diesel fuel contains paraffins that congeal in cold weather, forming a wax-like substance that blocks fuel flow. This occurs at lower temperatures than icing.
  • Fuel stability – Diesel fuel stored for long periods can become unstable and break down, forming gums that clog fuel filters and create fuel injector and combustion chamber deposits.

Diesel fuel additives help combat these issues. Automakers, however, caution to use additives as short-term solutions for specific issues, and not on a continuous basis.

What to know when using diesel fuel additives

  • Measure twice and treat once. Additives are designed to work with specific quantities of fuel. For example, 16 ounces of additive may treat 30 gallons of diesel fuel. Over-treating a fuel system with too much additive can damage expensive fuel injectors and the injection pump.
  • Get more for your money. Many additives bundle multiple treatments into a single product. For example, a diesel fuel “conditioner” may include the ability to absorb water, an anti-gel agent and a fuel stability enhancer in one bottle.
  • A large number of high-quality diesel fuel additives are available from the aftermarket. Before you purchase any product, consult your owner’s manual for any special precautions related to using additives.
  • Automakers test and recommend their own brand of diesel fuel additives or those of a designated provider. Keep in mind that using a non-approved additive could void the fuel system or engine warranty if an occurring problem can be linked to the additive.

Learn more about diesel engines, fuel systems and different types of additives in AAA’s latest Automotive Technology Update on Diesel Fuel Additives.

Find a quality service facility

Whether you need service on a diesel or gas engine, choose a AAA Approved Auto Repair facility and get the job done right the first time by a certified auto technician. To know approximately what a repair will cost, use the online tool to calculate the estimated price including parts and labor and the AAA member discount.

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