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A better understanding of fuel additives

By on November 4, 2015

Every driver knows that you put additives in your fuel, especially in winter. But how do you select from all the brands available? How much do you use? When do you use them? And how do you determine if they’re cost-effective?

These and other questions have concerned truck operators almost since trucks started using diesel fuel. Much of it has to do with the nature of the fuel itself.

Diesel is a mixture of hydrocarbon molecules. It varies slightly depending on where the crude oil, from which diesel is refined, comes from. It is affected by water and oxygen, both of which can change diesel’s physical properties. As it ages and oxidizes, it begins to form a thick sludge. The interface between diesel and water can become a breeding ground for organic particles from the air, the microorganisms that form the slime found in fuel tanks and clog fuel filters.

Additives address these problems and more, but with all the brands and types available (several hundred are registered with the EPA), how do you decide which is best for you?

In order to meet your needs, you’ll need to evaluate and prioritize those needs. To do that, you should understand what additives can do.

Winter operations

Two types of fuel problems occur in cold weather — freezing and gelling.

Fuel does not freeze, but any water in the fuel lines and filters does, slowing or stopping fuel flow to the engine. Gelling has a similar effect, but the mechanism is different. As temperatures drop, paraffin wax, a naturally occurring component of diesel, separates from the fuel. Its molecules bond together to form a cage-like structure that, as it grows, makes fuel more resistant to flow. It becomes a jelly-like substance rather than a pumpable liquid. Additives address both these problems by removing water from the fuel. That can be done in one of two ways: by emulsifying or de-emulsifying it.

Emulsifying involves chemically isolating water droplets at an almost molecular level so they remain suspended in the fuel and get pumped harmlessly through the system. De-emulsifying causes the water to form into increasingly larger drops until it becomes heavier than the fuel and drops to the bottom of the tank, safely out of the fuel.

If you’re using an additive that claims to emulsify water, be sure to check and, if needed, drain your fuel-water separator on a regular basis. It’s a good idea to do that anyway but especially with emulsifiers. If there is any cloudiness, you risk blowing out injector tips. That happens when water hits the heated tip in sufficient quantity to turn to super-heated steam. That expands the water from liquid to vapor with explosive force. It will do catastrophic damage to the injector, the piston and the cylinder bore.

My personal preference is for de-emulsifying additives. They effectively remove water from your fuel, preventing fuel line icing. As water drops out, it will accumulate in the bottom of the tank. It’s a good practice to drain water from your tank on a regular basis. Check to see if your tanks need draining with a water-detecting paste on the end of a clean stick.

How microorganisms gather and grow

Water enters fuel tanks several ways. You can usually protect from splashes when filling in the rain, but humidity comes in with air that replaces the volume of fuel burned. At night, when ambient temperatures drop, water condenses from the air and either mixes with the fuel or drops through it to collect at the tank bottom.

Along with moisture, microorganisms enter with the air. They draw oxygen from the water and nourishment from the hydrocarbon fuel. As they multiply, they create organic slime that clogs filters. Water control from additives helps control organics by creating a barrier between the water and diesel.

For more serious issues, turn to biocides that kill the organics. They should be used on a limited basis, perhaps only once or twice yearly. Biocides are packaged separately from additives for regular use because they are so toxic. If, and only if, you have a severe problem, use one only according to the EPA-approved instructions printed on the package or on an accompanying sheet in the box. Use protective gear when required and never exceed recommended dosages.

Stop gelling

The traditional method of delaying wax gelling was to blend Number 2 diesel with Number 1, also known as kerosene. This separates paraffin molecules so they are less likely to link together. But since kerosene is more highly refined, it is more expensive. And since the paraffin has a greater energy content than the rest of diesel, its removal lowers the energy in the resultant fuel, dropping fuel economy.

Anti-gelling additives are a more cost-effective solution. By introducing molecules that attach to the paraffin molecules, the additive delays the wax matrix formation, thus keeping the fuel liquid longer. Eventually, you can run out of anti-gel, depending on how much additive you use, but do not overuse. There are suggested ratios of additive to fuel. If you exceed the highest concentration, you run the risk of doing other damage to the fuel system. (Follow the directions. That’s why they exist.)

Among the problems you can encounter if you overtreat are compatibility with elastomers such as hoses and seals, filter plugging, corrosion of some metal parts and loss of lubricity.

Choose reputable brands

Some additives use solvents to carry their active ingredients throughout the fuel. Those solvents can react with older seals and hoses, causing them to become brittle, crack and eventually leak. Others, depending on their chemistry, would swell, soften and possibly dissolve.

For the last decade or so, reputable manufacturers have been using advanced, chemical-resistant elastomers like Neoprene and Viton. But there are still offshore suppliers that use inferior materials. They may meet dimensional and physical requirements, but lack needed chemical resistance.

Lubricity is needed to keep pumps and injectors operating smoothly. The process of removing sulfur, itself a natural lubricant, dries out fuel. Solvents add to the problem. Although biodiesel improves lubricity, it’s a good idea to check additive labels for the effects on fuel lubricity.

Some additives contain carrier chemicals that can, over time, corrode fuel system components with their precision machined metal parts. A complete fuel treatment should contain chemicals that protect from corrosion, or at least no chemicals that are corrosive.

Some additives can act too rapidly, resulting in fuel filter plugging. Detergents in additives dissolve carbon build-up. Detergents also help remove sludge from oxidized fuel from inside tanks. They are usually accompanied by dispersants, chemicals that keep what detergents dissolve from clumping together. If dissolved particles agglomerate or reattach, they can wind up clogging fuel filters.

General rules to follow

When selecting an additive, read the containers carefully. Look for what is claimed and compare it to what you need for your truck. Fuel purchased from a reputable truckstop, one that turns its fuel regularly, will be blended to flow at temperatures in its general area. Check weather forecasts for your destinations. If conditions will be colder, be sure to get an additive that will keep fuel flowing at your destination. If you encounter problems with icing in filters or in fuel lines, check the labels for water control. See what each says about controlling organic growth if that is a problem you’ve encountered. Organics are identified by slime in your fuel tanks or in your fuel-water separator.

Select the fuel treatment that best claims to address your problems. I advise sticking with nationally known brands that have stood the test of time. While there are many regional brands that may be quite good, there are also many that are not. I usually encourage entrepreneurs, but with your engine, too much is at risk. National brands have the ability to stand behind their warranties should anything go wrong.

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