Diesel Digest: Choose fuel additives carefully

May 9, 2018 by Capt. Jeff Werner

Diesel Digest: by Capt. Jeff Werner

Diesel fuel additives are an important part of a yacht’s fuel preventive maintenance program. There are many brands of diesel additives with a variety of formulations marketed to diesel engine operators. Selecting the best additive from the myriad products available requires a bit of knowledge of the components mixed in each additive’s formulation.

Chemicals – such as dispersants, surfactants, combustion enhancers and deposit surface modifiers – all target specific problems of contaminated fuel systems in tanks and deposits in engines, and they have unique benefits.

Before purchasing a diesel additive, conduct a little research to make sure it meets these minimum standards:

Remove engine deposits. Deposits in the combustion chamber keep the fuel from developing complete combustion, which increases fuel consumption. An additive component interacts with the surface of the deposit on a molecular level and lowers the energy needed to break its chemical bonds. The deposits can no longer adhere and will flake off.

Prevent deposit formation. Inhibi­ting the agglomeration of carbon chain molecules from forming heavy deposits results in smaller, lighter particles of contaminants in the fuel that are less likely to adhere to engine parts.

Reduce fuel consumption. The surfactant in an additive reduces the fuel droplet size, which enhances the combustion process, burning a higher percentage of the fuel before the exhaust valve opens. Using quality additives cuts fuel consumption by 5 to 10 percent.

Reduce emissions. As deposits are removed, pollutants such as carbon monoxide, oxides of nitrogen and sulfur, hydrocarbons and particulates are drastically reduced.

Reduce the carbon content of soot. This component limits combustion byproduct formation by enhancing carbon dioxide production. With less carbon available to end up in the ash complex, the amount of soot is greatly reduced.

Extend lubricating oil life. Additive-treated fuel produces smaller and less-abrasive particles, which result in cleaner, longer-lasting lubrication oil, and leads to reduced engine wear, and less maintenance and downtime, which lowers operating cost.

Enhance fuel lubricity. Naturally occurring sulfur in petroleum gives fuel more lubricity, but also contributes to air pollution. Since sulfur is removed from diesel fuel at the refinery to lower emissions, fuel lubricants must be added to avoid excessive wear of engine parts.

Inhibit corrosion. The acidic waste products of bacteria and mold living at the fuel/water interface in the fuel tank increase corrosion of the tank structure. Anticorrosion components limit that damage by forming a protective barrier on metal surfaces to prevent rust particles from developing.

Increase fuel stability. Chemicals which inhibit the oxidation of fuel and react to the acids and bases in the fuel all reduce fuel instability and give it a longer shelf life.

The normal aging process of the fuel is accelerated by microbial contamination. This leads to the build up of tank sludge, filter clogging and fuel breakdown. Surfactants and dispersants in additives help break down and dissolve tank sludge and biomass on tank walls.

Biocides may be necessary in cases of severe microbial problems. However, as the biocides kill the living bacteria and fungi, they just fall to the bottom of the tank. This dead biomass must be removed from the tank in the fuel polishing process to prevent continued filter clogging. Remember that biocides are extremely toxic and can be absorbed through the skin. Proper personal protective equipment should always be worn if a biocide is used in an additive.

Whichever fuel additive is best for a yacht’s particular circumstances, it should be used in the proper concentration every time the fuel tanks are topped off, when the fuel is polished and when the yacht is sitting at the dock for an extended period. Engine life can be more than doubled as the result of complete deposit removal, cleaner oil and reduced friction. Injectors, valves, rings and other associated parts will show less sign of wear, even after extended use.

Use of a proper fuel additive is a simple and inexpensive alternative to the cost of repairing severely damaged engine parts.

Capt. Jeff Werner, a 25-year veteran of the yachting industry, is a certified instructor for the RYA, MCA, USCG and US Sailing. He owns Diesel Doctor (MyDieselDoctor.com). Comments are welcome below.