What Temperature Does Diesel Gel? How to Ungel Diesel Fuel

gelled fuel filter
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’re someone who lives in Florida, southern California or perhaps Texas, the chances are good that temperatures are dipping below freezing and affecting the performance of your vehicle. If you happen to be driving a diesel vehicle, there is a unique risk of your diesel fuel gelling adding one more checklist item to consider for preventive maintenance. Read our guide to learn more or view our products to see how we can help!

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 #2 Ultra Low Sulphur Diesel that is common to all services stations, will ‘gel’ as the paraffin in the diesel fuel starts to crystallize and freeze. With long enough exposure to cold temperatures, it will produce a solid wax-like substance that can clog the entire fuel system. It’s similar to how a wax candle will remain solid until lit, at which point the wax progressively becomes a free-flowing liquid. Then, as it cools, the wax becomes solid again.

What Temperature Does Diesel Fuel Gel?

A similar process takes place in diesel fuel when the fuel begins to crystalize during cold weather. Once the weather is close to 10 to 15 degrees Fahrenheit*, gelling starts to occur and can clog the fuel system (*depending on the source and quality of fuel, gelling can occur as high as 20 degrees Fahrenheit).

How To 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 to Fix 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. Over 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. Fortunately, options exist that are much safer than spraying ether. Here are a few preventive tips:

    1. Heat: The best line of defense is to apply heat. Storing your vehicle in a climate-controlled garage or heated environment prevents susceptibility to freezing temperatures. Other tactics can range from a series of light bulbs under the vehicle emitting heat, wrapping the vehicle in a tarp with a heater blowing heat, to the modern-day block heater installed on the engine, keeping the vehicle protected from the frigid temperatures. The utility companies will love you too while racking up the electric bills.
    2. Kerosene: 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 this blend but in the southern regions with typically warmer temperatures, the #1 diesel may not be available. In either case, kerosene has its disadvantages as well, more than anything reduced fuel mileage and efficiency. If however, the truck stops running and the use of kerosene is the choice, it is highly advisable to let the engine run long enough to combine the fuels providing a steady flow of the mixture. Consider in a semi-truck for example, when working with 100’s of gallons of fuel in a tank, the time it takes for the kerosene to thaw the tank. The kerosene then also has to thaw the clogged fuel filter and frozen lines. It may take an hour of idle to thaw the entire line from the fuel tank, to the filter, to the injectors.
    3. Fuel Additives: There are now fuel additives that can provide an easy, low cost, and no-hassle solution to prevent gelling; one that any vehicle owner can do on their own. “When considering an additive, be sure to do your due diligence and compare all the products and claims,” Berg says. “It’s sometimes worth a little extra time and attention to find the best product. Just like wearing layers of clothes in the cold, additives are a way to add an extra layer of protection to prevent the wax in diesel fuel from getting thick.” Berg warns that many products use alcohol, and to research a product that provides not only adequate temperature coverage but also protection for the full system including lubricity, cetane, water dispersion, and a guarantee for success. 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°F.

How to Prevent Diesel Fuel Gelling?

So why take the time to prevent diesel fuel gelling? 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.

For those unable to heed the warning, no prevention has taken place, and gelling remains a possibility, or it has already taken place, emergency additives are also available! For example, Diesel Winter Rescue is a formulated product that reliquifies gelled fuel and de-ices frozen fuel filters to restore the flow of diesel fuel to the engine allowing the vehicle to be fully operational again. Products such as Diesel Winter Rescue are a helpful option to carry in your vehicle during the winter months, just in case.

“I sell quite a bit of Hot Shot’s Secret Diesel Winter Anti-Gel additive. It’s a tough sell because of all the diluted products out there on the market. I just tell people this works and it has a 100% money-back guarantee. I wouldn’t be selling this product, and I’ve never sold a product, that doesn’t show results.”   – David Berg