Like medicine, fuel additives can treat specific engine issues

Jul 28, 2015 by Capt. Jeff Werner

Cybersizzle, Hot Stuff, TNT-Ultra, The Force, Greased Lightning all sound like the names of energy drinks that should be part of the roll call that includes Red Bull, Monster and Rockstar. Actually they are the names of diesel fuel additives that are sold in the United States. And if you feel more comfortable buying an additive with a more descriptive name there is always Diesel Mechanic In A Bottle.

The federal Clean Air Act requires that manufacturers and importers of diesel fuel additives register their products with the Environmental Protection Agency (EPA) before they can be available for sale in the United States. The EPA database contains many thousands of different diesel additives all sold in bottles and jugs and marketed to diesel engine operators such as yacht captains and engineers.

The EPA list includes additives that are made in just about every state, and in the countries of Argentina, Australia, Canada, China, France, Georgia, India, New Zealand, Spain, Taiwan and the Ukraine, as well.

DIESEL afc710-allsizesv2

AFC 710 Fuel Catalyst is a broad spectrum diesel additive designed for Tier 4 engines. PHOTO BY AXI INTERNATIONAL

Tallahassee, Fla., even manufactures its own secret sauce, called appropriately enough City of Tallahassee Fuel Additive. And there’s someone in my old neighborhood in Brooklyn that is making a diesel additive, too.

How can you decide if you need a fuel additive, let alone which one to buy?

Diesel fuel additives are an important part of a yacht’s fuel preventive maintenance program. Not only do the additives help maintain the cleanliness of the fuel, they aid the combustion process and add stability to the fuel so it doesn’t degrade.

Chevron’s Diesel Fuel Technical Review, the authority for those of us in the diesel fuel business, addresses the use of aftermarket additives:

“It would be convenient for the user if a finished diesel fuel could satisfy all of his or her requirements without the use of supplemental additives. Although this is usually the case, some users require additional additives because the low-temperature conditions in their region are more severe than those for which the fuel was designed or because of other special circumstances. Other users feel they will benefit from using a diesel fuel with enhanced properties compared to using regular diesel. Finally, there are those users who regard the cost of an additive as cheap insurance for their large investment in equipment.

“A large number of aftermarket additive products are available to meet those real or perceived needs. Some are aggressively marketed with testimonials and bold performance claims that seem ‘too good to be true.’ As with any purchase, it is wise to remember the advice, caveat emptor, ‘let the buyer beware.’

“It may be helpful to regard additives as medicine for fuel. Like medicine, they should be prescribed by an expert who has made an effort to diagnose the problem, as well as the underlying causes.”

Given that the majority of aftermarket additives are blends of compounds, much like a multivitamin, what are the most important components to look for in a diesel fuel additive? The chemicals contained in the additive should enhance:

  •  Engine and fuel delivery system performance. Combustion catalysts reduce the black smoke that comes from incomplete combustion, while cleanliness additives keep injectors and combustion chambers free of soot. Lubricity enhancers compensate for the loss of sulfur, a natural lubricant, which is removed from ultra-low and low sulfur diesel. This added lubricity helps keep injector nozzles from getting damaged and giving a poor spray pattern.
  • Fuel stability. Chemicals that 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. Dispersants that keep small particles of organic contaminants from clustering into aggregates large enough to plug filters also extend fuel life in storage.
  •  Contaminant control. Dispersants act on large organic molecules, while corrosion inhibitors form a protective barrier on metal surfaces to prevent rust particles from developing and dislodging. 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 to prevent continued filter clogging. Remember that biocides are extremely toxic and they can be absorbed through the skin. Proper personal protective equipment should always be worn if a biocide is used in your additive.

Whichever fuel additive is best for your yacht’s particular circumstances, it should be added, in the proper concentration, every time the fuel tanks are topped off, when the fuel is polished and when the yacht sits at the dock for an extended period of time.

Capt. Jeff Werner has been in yachting for more than 20 years on private and charter yachts, both sail and power. He is an instructor for RYA, MCA, USCG and US Sailing courses and owns Diesel Doctor ( Comments on this column are welcome at


About Capt. Jeff Werner

Capt. Jeff Werner has been in yachting for more than 20 years on private and charter yachts, both sail and power. He is an instructor for RYA, MCA, USCG and US Sailing courses and owns Diesel Doctor (

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