What Temperature Does Diesel Fuel Start To Gel?

Colder temperatures and a correspondingly higher air density make it harder to start a diesel engine. Extremely cold temperatures can cause the diesel fuel to gel, rendering it unusable until it’s returned to a liquid state. 

This article explores the temperature at which diesel fuel starts to gel, what you can do to prevent diesel fuel from gelling, and how to de-gel diesel to get back on the road. 

What Temperature Does Diesel Fuel Start To Gel? 

Diesel fuel starts to gel at temperatures at or below 20 degrees Fahrenheit. However, there’s no exact temperature at which diesel fuel starts to gel. Gelling rates vary depending on the diesel fuel’s additives, quality, and environmental conditions. 

As the temperature drops, diesel fuel begins to take on an opaque and viscous appearance that indicates the onset of the gelling process. Diesel must remain at temperatures below -10 degrees Fahrenheit for roughly 48 hours before it gels completely. 

In fact, diesel fuel can gel while you’re behind the wheel. If you start to notice a decline in engine performance while driving in freezing temperatures, pull over and address the issue before continuing — or you risk critically damaging the engine. 

Why Does Diesel Gel? 

Diesel fuel gels due to the crystallization and solidification of paraffin wax — a component of diesel fuel — in response to extremely cold temperatures. As the paraffin wax begins to form a solid mass, it blocks any flow within fuel lines, filters, and pumps. 

The temperature at which diesel fuel begins to gel is called the cloud point. At this point, the paraffin wax particles start to clump together and turn the fuel cloudy, indicating that the gelling process has begun. 

Higher-quality diesel has a lower cloud point, which means it takes longer to gel. Conversely, lower-quality diesel has a higher cloud point. 

How Does Gelled Diesel Affect Your Engine? 

Gelled diesel fuel clogs up the fuel system components, and the problem only worsens as temperatures decline. Starving the engine of fuel causes significant issues, especially at higher RPMs. Without the diesel fuel to ignite the compressed air, the engine cannot operate as intended. 

If you’ve ever seen a diesel fuel filter covered in paraffin wax, you can understand why liquid diesel fuel has a hard time passing through the filter’s fine mesh and reaching the combustion chamber. It’s almost as if you had melted a candle over the filter or covered it in thick pancake batter. 

Symptoms of Gelled Diesel

Diesel vehicles with gelled fuel will refuse to start in extremely cold temperatures. If the diesel starts or is already running as the temperature drops, it will begin to perform sluggishly, accelerate slowly, and lack power. 

Even if the fuel pump sounds like it’s priming, there’s not enough fuel flow or quantity to support efficient engine operations. 

How to Prevent Diesel from Gelling

Diesel must be stored in a temperature-controlled environment to prevent it from gelling. Maintaining an acceptable temperature often means keeping your diesel vehicle or fuel supply inside. Aftermarket fuel additives can also lower diesel’s gelling point or cloud point. For those dealing with extreme winter conditions in Indianapolis, taking proactive steps to prevent diesel gelling is essential to keep vehicles running smoothly.

Store Diesel Properly

Store diesel at temperatures between 30 and 70 degrees Fahrenheit to prevent gelling. Keep a full tank of diesel to prevent moisture from entering. Diesel should be stored away from your living space but contained within a shed to prevent it from going bad.

Switch to a Winter Blend Diesel Mixture

In addition, many gas stations located in colder climates switch to a winter blend as the temperatures start to fall. These fuel blends contain diesel and anti-gelling additives to assist drivers traveling across the country. 

However, determining the exact fuel-to-additive ratio can prove challenging, so it’s a good rule of thumb to keep your own supply of anti-gel additives on hand.

Use Fuel Additives 

Fuel additives work best between the cloud point and the pour point, the lowest temperature at which diesel will flow before it starts gelling. This range of temperatures is called the cold-filter plugging point and describes the fuel’s trajectory toward gelling after reaching the cloud point. Introducing additives lowers the gelling point to improve cold-weather performance. 

Additives also contain a cetane improver. Cetane is a fuel’s ignition quality, or how quickly the fuel ignites. Higher cetane levels mean better cold starts due to fast fuel ignition.

Get into the habit of putting in fuel additives before temperatures are expected to drop. It’s best to put fuel additives in before filling up at the pump to ensure the additives mix well with the diesel. 

How To Remedy Gelled Diesel

Anyone who works in the fleets and transport industries knows that you can’t always predict or avoid cold weather. Diesel will reach its cloud point and begin to gel, causing delays. However, certain solutions can reverse the effects of gelling to help you get back behind the wheel and on schedule. 

Fuel Warming Devices

As the name suggests, a fuel-warming device ensures the diesel fuel is maintained at an optimal operating temperature to prevent gelling. Block heaters keep the engine and coolant warm but don’t necessarily warm the fuel directly. Heated fuel filters, in-tank fuel heaters, and fuel line heaters make all the difference in keeping diesel warm and functional. 

Fuel Filter Replacement

Diesel fuel filters typically catch most of the paraffin wax that solidifies. Replacing clogged filters with new ones can refresh the system, but it’s not an immediate solution. 

Instead, fill the fuel filter with half diesel and half anti-gel additives before reinstalling it and idling the engine until it reaches operating temperatures. 

Kerosene 

Adding kerosene to diesel lowers the cold-filter plug point. However, kerosene only dilutes the diesel fuel and the paraffin wax within. Therefore, kerosene doesn’t necessarily prevent gelling; it only prolongs the gelling process. 

Conquer the Cold With Cadence’s Premium Additives

Diesel provides the grit necessary for heavy-duty applications, but a significant drop in mercury can put almost anything out of commission and cause diesel gelling. Cadence offers superior fuel additives designed to protect your engine against the cold and prevent diesel gelling. Call us at 336-629-2061 to learn more about our top-quality products and exceptional services. 

Sources:

Use of diesel | U.S. Energy Information Administration (EIA)

Diesel Analysis and Specifications | Colorado Department of Labor and Employment

Pour Point | FSC 432: Petroleum Refining

SIGNIFICANCE of CETANE NUMBER in FUELS 460234 | SAE International