Diesel fuel gelling is the result of the solidifying of paraffin in the fuel during cold temperatures.

How to Prevent Diesel Fuel Gelling

For truck drivers, the winter months are more than just that risky season when they have to be extra careful in driving. In fact, the cold months pose a lot more problems for them, one of which is diesel fuel gelling.

Diesel fuel gelling happens when the paraffin usually present in diesel starts to solidify when the temperature drops. At 32 degrees, the wax in liquid form will crystallize and leave the fuel tank clouded. At 10-15 degrees, it will finally start to gel and clog the tank and fuel filters.

Diesel fuel gelling happens when the paraffin in the diesel solidifies due to low temperature.Gel Point and Pour Point in Diesel Fuel Gelling

Gel point is the temperature point at which the diesel finally turns solid and can no longer flow through the fuel lines. Pour point, on the other hand, is the factor which determines the temperature at which a fluid starts to solidify.

In order for the diesel to flow better again, the gel point temperature should be brought back to the un-gel point which is around the temperature of the pour point. Unfortunately, the solidified waxes usually remain solid until its remix temperature is used to finally remelt or liquefy it.

One of the symptoms of diesel fuel gelling is problems in accelerating.

Symptoms of Diesel Fuel Gelling

There are several signs that can tell you that your diesel has already gelled. One of these is when you are having trouble starting your engine. Diesel fuel gelling clogs the fuel lines and fuel filters, preventing the fuel to pass through them. This phenomenon then prevents the engine from starting.

Another sign is when there is a difference in the fuel rail pressure. This is likely the cause of problems like sluggish performance and inability to accelerate properly. Here, a difference between the desired fuel rail pressure and actual rail pressure is observed when accelerating. In these cases, the desired pressure usually spikes up while the actual pressure remains low because of the diesel fuel gelling stopping the fuel from getting where it should go.

Kerosene helps prevent diesel fuel gelling by lowering the viscosity of the fuel.Ways to Prevent Diesel Fuel Gelling

Adding Kerosene

It is a common practice for truckers to mix #1 diesel which has a blend of kerosene with diesel #2 which is used on road applications. Kerosene helps in lowering the plug point temperature of the fuel and reduces its viscosity, therefore making diesel less likely to gel even during low temperatures. Places in the extreme cold zones usually provide a winter diesel fuel mix like this. Unfortunately, it is not that easily available on places down south when hauling north.

Going on Engine Idle

Now if you go asking around, you will probably hear drivers suggesting to keep the engine running to keep the fuel from gelling. While this may work, it is not recommended at all for a couple of reasons. Not only does it negatively affect fuel use, it can also lead to engine wear, tear and excessive emissions.

Emergency Gear

Extra gear can help lessen the risk of diesel fuel gelling. Here, extra filters are needed to accommodate a cold flow treatment and a diesel emergency treatment. The cold flow treatment is used before going into the cold zone to prepare the fuel. The diesel emergency treatment, on the other hand, melts the gelled paraffin to get the fuel flowing again.

Additives and Fuel Treatments

Additives and fuel treatments are another common solution used to address diesel fuel gelling. Just like the earlier options mentioned, they also work to reduce the formation of paraffin crystals. They also lower the pour and gel point of the fuel as well.

A good example of a fuel treatment is CleanBoost® Sno-Cat™ Diesel Fuel Conditioner which is designed to reduce pour points and diesel fuel gelling in #1, #2, and even B5 and B20 Biodiesels. This quality additive is made with a unique blend of copolymers and fuel catalyst that prevents the formation of crystals. The way it works is that it prevents fuel system plugging by modifying the very crystals that usually form in the fuel during low temperatures. The crystals formed are smaller in size with the help of this additive, therefore preventing waxing and diesel fuel gelling. This product, moreover, also has a pour point depressant chemistry that improves the flowing capabilities of the fuel.

Additives like Sno-Cat™ also offers filter plugging prevention and stops water-related problems in the fuel. In addition to this, this product also increases range of the crude oil to be used in middle distillate production. Fuel technologies like these are also very helpful to those who don’t always have access to kerosene because it reduces the need for kerosene dilution in the fuel. It is also an EPA registered product so you are assured that you are also doing the environment a favor when using it.

Generally, fuel additives like Sno-Cat™ helps boost fuel economy by making the diesel fuel more efficient. It also helps trucks run smoother and longer during those winter hauls with its specialized wax forming prevention function.

If you want to know more about this product, simply go here.

Want a quick and easy solution to thaw gelled diesel fuel in an emergency? Read on to learn what to do in emergencies.

19 Responses to How to Prevent Diesel Fuel Gelling

  1. […] fuel gelling is a very common problem for many drivers during the winter season. On our article “How to Prevent Diesel Fuel Gelling”, we talked about the reasons behind fuel gelling, its impact on vehicle performance and how to […]

  2. The diesel fuel in my truck starts to gell all the time because of the cold climate I live in. I've never heard of adding kerosene to the fuel to help stop the gelling before. It makes sense as you point out that it reduces it viscosity therefore making it a lot less likely to gell over. I'll definitely have to try that in my truck sometime soon.

  3. Tech Guy says:

    Hello Dave,

    Having seen firsthand the results of CleanBoost® Sno-Cat™ in stopping diesel fuel from gelling at extreme cold temperatures, I would recommend you give that a try as well. It’s very cost efficient and helps the entire fuel system. Here’s a handy link if you’re interested:

  4. Trent says:

    What is a safe temperature to start using the block heater and how long should I leave it plugged up?

  5. Tech Guy says:

    Hello Trent,

    Excellent question! As a general rule, you are safe to use a UL approved engine heater for temperatures at or below 40 degrees Fahrenheit. As far as how long should you leave it plugged in for… I would not leave it plugged in for more than 48 hours concurrently. Longer than that, I would recommend you start your vehicle and drive it to get all the fluids circulated throughout. If when you park it again you need to use your block heater, same general guidelines should be followed.

    Most outdoor electrical receptacles are GFCI (ground fault circuit interrupter) protected in the event of water intrusion to the circuit which in turn can cause a short circuit condition. However, these can be a little touchy when it comes to higher current draws of a block heater. Best to check it periodically and use it as outlined above. This way your vehicle’s engine will be warm enough to start when those colder temps hit. Best of luck!

  6. Rodney Babb says:

    How much Kerosene should I add to my tanks? I have 2 100 gallon tanks but of course they don’t hold the full 100 gallons. What should the ratio be?

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  8. Tech Guy says:

    Hi Rodney,

    If you’re already gelling up, you can go as high as 25% by volume. However, to prevent gelling and have the engine perform better, it’s best not to exceed 18% by volume. Hope this helps and keep us posted.

  9. Maggie Allen says:

    Thanks for sharing this post on preventing gelling in your diesel engine! I had no idea that keeping the engine on idle could end up being more problematic than helpful! It sounds like the best thing to do is to have lots of kerosene and additives in your truck at all times if something is going wrong. After all, it's better to be safe rather than sorry!

  10. Tech Guy says:

    Thanks Maggie! Great to hear from you in Fairbanks!

  11. Carthy Joseph says:

    This is great information, do you know for the Freightliner Cascadia 2016 with a DD15 engine if it is safe to add additives. I was told it could void the warranty, I travel regularly between Canada and Texas and do have concerns with gelled fuel.

  12. Tech Guy says:

    Hello Joseph,

    The key is to use a quality, EPA approved additive such as CleanBoost® Sno-Cat™, which will not void the manufacturers warranty. Hope this helps!

  13. sadegh says:

    i want to know about the addetive for gelling the gasolin and so ungelling that.
    can you help me please?
    please send to me in private email if you can?

  14. Tech Guy says:

    The best solution for gasoline freeze ups, would be a product called HEET, sold at most auto parts stores. Thanks and good luck.

  15. Jack says:

    Is there a rule of thumb (or exact calculation) for how quickly the engine/fuel will cool toward gelling at a given temperature? Specifically, if the truck is warm when arriving to work in the morning, can the block heater remain unplugged for 8-9 hours until quitting time? For purposes of this question, let’s say the temperature hovers around 32-degrees and the pickup is parked outside.
    Thanks in advance!

  16. Tech Guy says:

    Hey Jack,
    There isn’t really a rule of thumb on this since variables of humidity and wind speed calculate into fuel gelling. Even if the fuel filter is in an area more prone to the wind, will affect gelling times, along with any remaining water (condensation) in the fuel filter or system.​

  17. I live in Wisconsin and have never gelled up on any of my diesels trucks, tractors, or equipment. I use an additive starting in September with new filters and draining tanks and separators.

  18. Julius Wither Amberfield says:

    It was nice that you explained that diesel fuel gelling will clog the fuel filters and lines and prevent fuel from passing through them. That sounds like a problem that can cause my car to break down in the middle of the road. My brother knows a few things about cars, and he mentioned that I need to take mine to the diesel mechanic soon because it’s having troubles accelerating. I know that I can trust his advice so I will. Thank you for sharing.

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