When the weather gets frigid, water isn’t the only thing freezing. In winter weather, drivers and fuel management professionals also need to be aware of the potential for their diesel fuel to gel.
Diesel fuel gels in cold temperatures because it contains paraffin wax, a normal fuel component that improves fuel viscosity and lubrication.
When outside temperatures begin to fall, this paraffin wax starts to become insoluble, appearing as little crystals in the fuel. If it stays cold enough for long enough, the wax will thicken the diesel fuel. This is part of a phenomenon called "diesel fuel gelling," in which the problem can become so advanced that the paraffin wax can clog fuel filters to the point where the fuel will no longer flow, basically rendering your engine useless.
Diesel fuel gelling has the potential to occur when temperatures drop below the fuel's cloud point. The exact temperature it happens at will vary from fuel batch to fuel batch. Speaking in generalities, the two major pipelines supplying fuel to much of the eastern part of the country normally provide diesel fuel with cloud points between 16 and 20 degrees F.
How do you prevent your diesel fuel from gelling? It’s essential to ensure that your diesel engines continue to work as they should in these cold winter temperatures. Here's a look:
A primary way to prevent diesel fuel gelling is to control the temperature of the facility in which the engine is being stored. When the engine is running, the fuel is moving and flowing and cannot solidify. Storing your vehicle or equipment in a heated garage or climate-controlled structure is enough to do the trick. However, this option may not be realistic for many.
Mixing in amounts of kerosene with diesel fuel reduces the plug point temperature or the temperature at which paraffin wax crystals solidify and begin to clog fuel filters. The protection, if you want to call it that, increases by the percentage of kerosene blended in. The benefit is fuel-dependent, but you might expect a 3-4 degree drop in plugging temperature for every 10 percent kerosene blended.
Many winter climate fuel suppliers will offer diesel fuel that's already pre-mixed with kerosene for user convenience.
Adding a winter diesel fuel additive is one of the easiest and most popular ways to prevent diesel fuel gelling. These additives can prevent the paraffin wax from gelling together and solidifying. Many fuel additives also offer other winter weather benefits, such as helping improve cold engine starts and removing harmful deposits from your vehicle’s fuel injectors.
Professional fuel users have a good idea when they need to add a cold flow improver because they generally know the cloud point and plug point temperatures of their fuel. They keep track of outside temperatures so that they have an idea ahead of time when they need to break out the cold flow improver (since it needs to be in the fuel before the fuel gets too cold).
In general, satisfactory operation should be achieved in most cases if the blended fuel is 6 degrees C above the "10th percentile minimum ambient temperature" for the fuel's area. This term may not mean anything by itself, but it's supposed to be the temperature that isn't supposed to be below for more than 3 days out of a given 30-day period. This is different for different areas and different times of the year. For example, Long Island's 10th percentile temperature in December is -14 degrees C. For Alabama in December, it's -6 degrees C.
As a user, you want to start considering cold weather treatment when the temperature starts coming within 5 degrees of your fuel's cloud point. This means, if you're tracking the ambient temperatures for your area when the forecast starts projecting lows that approach 10 degrees above the normal 10th percentile minimum ambient temperature, that is the time for you to get your cold flow improver into the fuel.
During the harsh winter months, you will find that your vehicle, equipment, and diesel fuel need a little more care. Failure to take the proper precautions, such as adding kerosene, storing the diesel engine in a temperature-controlled facility, or implementing a fuel additive can take your diesel engine out of service.
How are you preventing gelled diesel fuel? Don't ignore this crucial part of your diesel engine maintenance.