Diesel Fuel Additives

By Brian Stern

For those who are new to trucking or didn’t grow up working on engines, the concept of fuel additives can be a confusing one. And it is certainly not something covered in most trucking schools. We turned to Brian Stern, Director of Sales for Stern Oil Company who is our local oils and lubricant supplier so he could explain some of the basics of fuel additives: why they are important and the purpose they serve.

What are Fuel Additives?

Fuel additives have been referred to as “mechanics in a can.” While we certainly don’t believe they can replace a good maintenance schedule with qualified mechanics, high quality fuel additives definitely reduce maintenance costs and help your engine run more efficiently.

Fuel additives are essentially chemical compounds that have been formulated to increase fuel efficiency and improve the quality of your fuel so that there is less wear and tear on your engine. While US diesel is good, it is formulated to meet emissions standards, not mechanical standards. 

Generally speaking, fuel additives that have good detergents and stabilizers, lubricity agents, and corrosion inhibitors (details below) will enhance the performance of the engine and provide for a more “complete” combustion of the fuel. This will inherently lead to a longer life of your engine and your filters and less downtime.

Cost of Additives

These additives should cost no more than 1-2¢ per gallon for summer fuel and no more than 2-4¢ for winter fuel. The proper additives used correctly should pay for themselves in better performance of the engine and reduced maintenance and downtime.

Year-Round Diesel Fuel Additives

We believe any year-round additives you select should provide the following benefits:

1. Detergent package (maintains optimal combustion)

A detergent package scrubs your engine of carbon build-up on your engine and parts. Carbon build-up can disrupt the airflow in your engine affecting your fuel economy, increasing emissions and causing incomplete combustion. Detergents keep the carbon moving through the engine so it doesn’t build-up and cause issues. Make sure that any detergents you use meet the Clean Up Rating of the DW10 Standard Injector Coking Test.

2. Fuel Stabilizers and Anti-Oxidants (prevents premature filter plugging and maintains power and fuel economy)

When fuel gets hot and is pressurized by an engine it produces asphaltenes as a byproduct. Yes, this is chemically related to asphalt that covers our roads! These asphaltenes easily plug fuel filters and can lead to unplanned downtime by shutting down your truck. Fuel stabilizers and anti-oxidants help keep these asphaltenes from forming. If you are buying an additive make sure it passes ASTM D-6468.

3. Lubricity Additives (extends life of fuel pump and injectors)

Fuel injection pumps and injectors are designed to work seamlessly. But without proper lubrication the spots where metal parts of the engine meet will gradually wear down. Lubricity additives lubricate your fuel increasing the life of both your fuel pump and injectors. Make sure that your lubricants pass the ASTM D-6079 to have a 460 micron wear scar or less.

4. Corrosion inhibitors (preserve life and performance of fuel system)

If you’ve ever owned a cast iron skillet then you probably know that without a layer of corrosion inhibitors the iron will begin to corrode and rust. But, keep your cast iron pan well-protected and it can be used for generations. Similar to a cast iron pan, your tractor’s metal engine parts are easily corroded by air and water if not protected.

Diesel Fuel Additives for Winter

The following benefits pertain specifically to winter fuel additives. Any winter formulation should provide all of the above benefits as well as the following:

1. WASA, or Wax Anti-Settling Agents (prevents filter plugging in winter temperatures)

All diesel fuel contains wax. Normally this wax is liquified, however as temperatures plummet, these wax particles may begin to crystalize. Wax anti-settling agents keep these wax crystals small and in suspension rather then allowing them to settle at the bottom of the fuel tank.

If you’ve ever heard your mechanic talk about the dreaded “engine gel” that can happen when a cold engine sits, it is caused by these wax particles settling at the base of the tank and entering the fuel system.

2. Cold Flow Improver (prevents filter plugging in winter temperatures)

A cold flow improver works hand in hand with WASA by changing the molecular structure of the wax crystals making them less likely to interlock and form larger crystals. This keeps the flow of fuel moving in your engine.

3. De-Icer With a Glycol Ether Formulation (prevents formation of ice in the engine)

All diesel fuel contains a small amount of water. The cooler the fuel, the more the water separates from the fuel. As temperatures drop, water can completely separate and fully drop out of your fuel. This water then settles in the fuel tank and forms ice crystals that plug fuel filters. In fact, 90% of filter plugging issues are water-related.

The glycol ether de-icer lowers the freeze point for water so that it does not easily form ice crystals. Most de-icers provide protection down to -35F. It is important that any de-icer you use not contain alcohol. You do not want alcohol in diesel fuel because alcohol can be corrosive to the metal in the engine and cause premature failure of your fuel injectors.