As any qualified mechanic will attest, one of the principal concerns about driving a diesel vehicle is the potential for fuel gelling at cold temperatures. This makes it difficult or impossible for fuel to pass through the engine, resulting in operational problems. If you are a first-time diesel vehicle owner, you may have questions about this issue. Below are answers to some of the most common so that you can prepare.

A Guide to Diesel Fuel Gelling

Why does diesel turn to gel?

Diesel fuel contains paraffin wax, which improves lubrication and viscosity. Although it is normally in liquid form, under cold temperatures, the wax starts to solidify. First, the fuel turns cloudy, then begins to resist flow, and eventually crystallizes into a gel. This cannot pass through the fuel filter or hoses of the vehicle, preventing it from starting.

How cold must it be for diesel to gel?

Diesel fuel #2, also known as standard diesel, has a lower freezing point than water and will start to gel at about 17 degrees. It is inexpensive and flows well under normal conditions. However, #1 diesel—sometimes called premium or winter diesel fuel—is less viscous and less prone to freezing when temperatures drop. It may withstand gelling in temperatures as low as -40 degrees.

How can you prevent diesel gelling?

mechanicKeep the engine compartment warm by parking your truck indoors or installing an engine heater. Also, use premium or winterized diesel fuel, which you can find at many service stations.

You can even add a non-alcohol additive called a "cold flow improver," which prevents the wax from sticking and blocking the flow. Finally, keep your tank as full as possible. This prevents condensation from forming, which can freeze when temperatures drop. 

What are the symptoms of diesel gelling?

Gelling may cause numerous symptoms that require a mechanic to solve. For instance, you may have trouble starting the vehicle, or the engine may start and then immediately die. If the truck does start, you will likely notice that it cannot accelerate efficiently. Finally, if your truck has a fuel pressure gauge, it will show that you are getting low or no pressure. 


If you need an experienced mechanic for your new diesel vehicle, contact Stephenson Truck Repair in Lincoln, NE. They are locally owned and have been serving Lancaster County clients since 1966. They specialize in truck service and collision repair, including truck paint and RV body work. Learn more about their services on the website. Call (402) 466-8532 to discuss your questions with a mechanic.