What Temperature Does Diesel Gel? How to Ungel Diesel Fuel

October 21, 2022

What To Do If Your Diesel Fuel Gels

As the cold sets in for the winter, many around the country start thinking of their vehicles and the need for winter maintenance. Unless you live in Florida, southern California or perhaps Texas, the temperatures are probably dipping below freezing and affecting your vehicle’s performance. 

If you drive a diesel vehicle, you must consider diesel fuel gelling as part of your preventive maintenance routine. Diesel fuel gelling is a unique risk to diesel engines, and it can significantly impact your vehicle’s ability to start. Learning about fuel gelling and how to prevent it can help you prepare for winter, drive with ease and have peace of mind that your diesel vehicle is in excellent shape.

We recently caught up with someone who is an expert on winter maintenance to get his advice. David Berg of BayBrook Solutions lives in Mandan, North Dakota, where at the time of this writing the weather was a balmy 5°F with a 20 mph wind.

“I’m wearing my gloves rated for 40 degrees below zero, and my hands are still very cold,” says David. “We’ve been lucky this year though. So far we have only been down into single-digit temps. By now it’s often 20 degrees below zero here for days and days on end. Brain freeze can happen just by being outside. We used to own a towing company and unfortunately for our customers, we have seen plenty of gelling causing diesel vehicles to not start in the winter.”


Why Does Diesel Fuel Gel?

Diesel fuel, especially the common #2 Ultra Low Sulphur Diesel sold by service stations, will ‘gel’ if the paraffin in the diesel fuel starts to crystallize and freeze.  With long enough exposure to cold temperatures, it produces a solid wax-like substance that can clog the entire fuel system. The fuel solidifies and loses its ability to flow. Diesel fuel gelling is similar to how a wax candle remains solid until lit, at which point the wax progressively becomes a free-flowing liquid. Then, as it cools, the wax becomes solid again.


At What Temperature Does Diesel Fuel Gel?

Diesel fuel gels when temperatures fall below 10 to 15 degrees Fahrenheit or -12 degrees Celcius. If engine complications occur at temperatures above 10 to 15 degrees Fahrenheit or -12 to -9 degrees Celcius, the issue is likely due to ice rather than gel. However, gelling can occur at temperatures as high as 20 degrees Fahrenheit if the engine runs on low-quality fuel.


How Can You Tell When Diesel Fuel Begins to Gel?

Berg mentions that there are a few telltale signs when diesel fuel is beginning to gel and it’s all primarily based on the loss of power and compression because fuel is failing to reach the combustion chamber. If you could see the fuel, it will have a cloudy appearance; which is an indicator that gelling has already occurred. 

Other signs to look for are white smoke from the exhaust when trying to accelerate, or if you are sitting idle trying to throttle and the engine stops running. Also, if the vehicle starts, but won’t continually run, then this too could be a sign that your fuel has gelled. Whether it’s the lack of RPMs when an engine is running, or it’s one of those cold winter mornings and the truck just won’t start at all, gelled diesel fuel is probably the culprit.


How Can You Prevent Gelled Diesel Fuel?

When your diesel vehicle won’t start at all, many make the mistake of grabbing a can of ether to begin the combustion process. There are some risks with this solution, however, as there may be no fuel to actually ignite. Spraying too much ether and having un-contained ether spray creates even more problems. 

The un-contained spray could ignite other hot components causing engine damage, or putting too much ether in the fuel line could simply ignite air in the lines rather than fuel which could also badly damage the diesel engine. Prevention is more effective than waiting until your fuel gels, and options exist that are much safer than spraying ether. You can prevent gelled diesel fuel with the following solutions:


Heat can help prevent fuel gelling by reducing your engine’s exposure and vulnerability to cold temperatures. You can protect your vehicle with the following solutions:

  • Warm storage: Storing your vehicle in a climate-controlled garage or heated environment protects it from freezing outdoor temperatures.
  • Light bulbs: Placing light bulbs under your vehicle allows them to emit heat and keep your engine warm.
  • Tarp and heater: Wrapping your vehicle in a tarp and running a heater that blows heat can warm your vehicle overnight.
  • Block heater: a block heater connects to your engine and warms your engine’s coolant, keeping your oil warm to prevent freezing.

When you use heat to prevent freezing and gelling, you must also consider energy consumption and how to protect your vehicle away from home. Storing your vehicle in a climate-controlled garage is an effective way to protect it while you’re at home, but it can quickly increase your energy bill. Light bulbs, heaters and block heaters require electricity to work, so you may need to consider other methods if you want to protect your vehicle while keeping energy bills low.

You also need to protect your vehicle while it sits at your workplace throughout the day or when you leave it in a parking lot during travels or vacations.


With the challenge of staying warm at 20 degrees below zero, folks still have a couple of other options by modifying the fuel mixture itself. The most common use is pouring kerosene into the fuel tank to lower the point of freezing. To further take advantage of the lower freezing point of kerosene, many often mix #1 diesel, which blends kerosene with #2 diesel fuel. 

The northern regions of the country often provide #1 and #2 blended diesel fuel, but #1 diesel may not be available in the southern regions with typically warmer temperatures. In either case, kerosene has its disadvantages, such as reduced fuel mileage and efficiency. 

If your truck stops running and you choose to use kerosene, it is highly advisable to let the engine run long enough to combine the fuels properly and provide a steady flow of the mixture. For example, a semi-truck contains hundreds of fuel gallons and requires a considerable amount of time for kerosene to thaw the tank. The kerosene must also thaw the clogged fuel filter and frozen lines. It may take an hour of idling to thaw the entire line from the fuel tank to the filter and the injectors.

Fuel Additives

Newer fuel additives serve as easy, low-cost and hassle-free solutions to prevent fuel gelling. With the right fuel additive, you can avoid and solve engine complications without making expensive repairs. Using only the highest-quality fuel additives is essential to protect your vehicle effectively.

Additives provide temperature coverage to help prevent your diesel fuel’s wax from thickening, but you should choose an additive that also improves your fuel’s water dispersion, lubricity and cetane to ensure it’s successful. Many preventive offerings are available, with some top choices immediately available such as EDT+ Winter Defense and Diesel Winter Anti-Gel promoting coverage down to -40 degrees Fahrenheit. Diesel Winter Anti-Gel lowers your fuel’s cold filter plugging point (CFPP) to prevent your fuel lines and filters from clogging.


Do You Need to Add Anti-Gel to Diesel Fuel?

Taking the time to prevent diesel fuel gelling is essential because it helps you save time and money by preventing more serious complications. Adding anti-gel to diesel fuel is a cost-effective solution to prevent your vehicle from breaking down.

Berg says, “If a tow truck is called, you may still be stuck with a vehicle that won’t run after paying the tow fee. In the case of a personal or small-duty vehicle, you can save yourself the lost $80 and the hassle, or in the case of a semi, the $500 price tag for a tow and lost time headed down the interstate. Instead, for only a few dollars in prevention and an easy pour into the tank, taking advantage of the top scientific additives could keep you from being stranded in the cold.


Will Gelled Diesel Thaw?

Gelled diesel fuel can thaw if the engine’s temperature returns to normal. However, thawing your engine may not be an option if it breaks down on the road or you lack a heated space to store your vehicle. Emergency fuel additives can help thaw gelled fuel inside the fuel tank.

Emergency additives are available if you skip prevention and fuel gelling occurs or remains a possibility. Hot Shot’s Secret offers Diesel Winter Rescue to help you solve gelling and icing issues.

Diesel Winter Rescue is a formulated product that thaws frozen filters and reliquifies gelled diesel to restore the engine’s fuel flow. This high-quality product restores full operational capabilities to an engine. Products such as Diesel Winter Rescue are a helpful option to carry in your vehicle during the winter months in case complications arise.


Prepare Your Diesel for Winter With Hot Shot’s Secret’s Diesel Winter Anti-Gel

Understanding how to prepare your diesel for winter can help you keep your vehicle running on the coldest days. The most effective way to protect your vehicle from freezing temperatures is to lower your fuel’s CFPP with a high-quality additive. Hot Shot’s Secret offers EDT+ Winter Defense and Diesel Winter Anti-Gel to reduce your fuel’s CFPP and prevent your fuel filters and lines from clogging.

EDT+ Winter Defense andDiesel Winter Anti-Gel also boosts your fuel’s cetane number and improves your fuel’s stability, winter operability, detergency and lubricity. Purchase Diesel Winter Anti-Gel online or locate a store near you to start preparing for winter.