When Does Diesel Fuel Gel and How to Prevent It?

Last Updated on January 28, 2023

If you make good use out of diesel fuel all year round, there’s two questions you’re bound to wonder – when does diesel fuel gel and how to prevent it? 

Diesel fuel use can be problematic when temperatures drop below freezing. This type of fuel—specifically, the most popular diesel fuel—#2 Ultra Low Sulphur Diesel, begins to get cloudy as the paraffin wax inside begins to stiffen. And then, depending on the exact composition, it freezes—becomes a gel—somewhere between 10 and 15 degrees Fahrenheit.

Diesel fuel is similar to wax. When wax is warm, it’s a liquid, and when it cools, it solidifies. Diesel is similar except that it remains a liquid at lower temperatures than wax. 

Gasoline, on the other hand, freezes at about -100 degrees Fahrenheit, so owners of gasoline-powered vehicles don’t have to be concerned about their fuel freezing. However, owners of diesel-powered vehicles and equipment must take precautions to prevent their fuel from freezing. 

How do you know diesel fuel has gelled?

When diesel fuel gels, it clogs the fuel tank and fuel lines. This can cause damage to the fuel lines—damage that needs to be addressed before driving. 

Signs your diesel fuel has gelled include:

• White smoke emitting from the exhaust when accelerating
• When idling, the engine cuts out when you throttle 
• The vehicle or machine starts, but won’t continually run

If you see any of these signs, or you know the external temperature will be below freezing, there are measures you can take to avoid frozen diesel fuel.

How to prevent gelling 

The first action you can take to prevent fuel from gelling is to park your vehicle or equipment somewhere temperatures don’t get too cold. For example, an insulated garage or equipment shed will be many degrees warmer than the temperature outside. Once you’ve warmed up the engine, drive outside and diesel fuel won’t gel when the engine is running. Even if you’re just idling the engine in a cold temperature for a long period of time, the fuel will remain in liquid form. 

If this isn’t an option, putting a tarp over the part of the vehicle or machine that houses the engine will keep the engine several degrees warmer. If you’re in an area where the temperature on the coldest nights reach the teens, this could be your best option. 

Another tool at your disposal—you can add a fuel additive designed to lower the temperature at which diesel fuel gels. 

This temperature is known as the fuel’s pouring point—the point at which diesel fuel can no longer be poured due to it having solidified.  

The pouring point for diesel fuel is between 10 and 15 degrees Fahrenheit. Adding a fuel additive changes the pouring point to between -30 and -25 degrees Fahrenheit. The additive also disperses water, which can freeze inside fuel lines and block fuel from reaching the engine. 

A diesel fuel additive chemically alters the size of the crystals that form in fuel during cold weather—the same ones that cause diesel fuel to gel.

Alternatively, you can add some kerosene to your fuel. Kerosene contains far less paraffin, so it freezes at a much lower temperature (-40 degrees Fahrenheit). Adding kerosene also significantly decreases the pouring point of diesel fuel. 

Both kerosene and diesel fuel additives decrease the fuel efficiency of the vehicle or machine. Kerosene decreases fuel efficiency more than diesel fuel additives and they tend to be more expensive, so kerosene is the less popular option. 

Both kerosene and diesel fuel additives can also be used to thaw diesel fuel once it has gelled. Simply add some to your fuel tank, and then, depending on the size of the fuel tank, wait 20 to 30 minutes to start the engine. Next, let the engine idle for another 20 to 30 minutes before driving or operating. 

Look for white smoke and the other above mentioned signs your engine isn’t getting enough fuel. If you see any of those signs, turn off the engine to allow the additive or kerosene to do its job. If more than enough time has passed by and, when you run the engine, you see signs it isn’t getting enough fuel, check your fuel lines for damage. 

You can also switch to #1 Diesel fuel, which has a higher concentration of kerosene in it. It’s sometimes known as winter diesel fuel. This kind has a pour point significantly lower than #2 Ultra Low Sulphur Diesel. 

Finally, you can use a block heater. A block heater is an electric-powered heating element attached to the engine block (on the vehicle or machine). A wire extends from the block, which you plug into an outlet. Once plugged in, the block heater warms the engine, which allows for an easier start. Heat the engine any time the temperature is expected to drop into the teens or you won’t operate the vehicle/machine for hours. Many people plug their cars in overnight for hassle-free morning starts and faster cabin heating and faster windshield defrosting.  

Diesel engine winter maintenance

Ensure the engines on your machines remain clean and dry. And be careful spraying under hoods. Modern machines come equipped with numerous electrical components that may become disconnected or damaged from a high-pressure spray. Run the engine shortly after spraying in order to dry it. 

Plan out your maintenance. Depending on your climate, winter weather can shut down operations for days or weeks at a time. Schedule maintenance when you expect weather to shut down operations. Quarries in northern climates, for example, shut down operations for four to eight weeks starting in January. By scheduling maintenance at this time, they decrease equipment down time. 

Test the batteries in your equipment fleet. Batteries don’t perform as well in cold temperatures. If batteries aren’t working at near capacity, you may want to swap out the batteries before temperatures reach their lowest. 

Also, when the temperature drops to freezing, it’s time to switch your regular diesel fuel for a winter performance fuel. This will allow you to work in colder temperatures without performing time-consuming tasks to thaw your fuel. This also applies to the machine’s hydraulic engine oil and lubricants. Switch to products that are designed to perform in cold temperatures. Stock up on anti-freeze and use as necessary. 

Sample machine oil near the start of the winter season. This will help with determining when the engine oil will degrade to the point of needing replacement.

Check the diesel fluid and diesel exhaust fluid (DEF) fill necks to ensure they are clean too. 

Diesel fuel winter storage 

Diesel fuel is expensive. In order to decrease and moderate fuel costs, numerous construction companies purchase fuel in bulk and store on site. 

You need to ensure the tank in which the fuel will be stored is clean, as well as any lines going into or from the tank. It needs to be airtight, so no contaminants can get inside. 

When the temperature drops, the fuel in your storage tank(s) are susceptible to freezing. 

There are a few options for preventing frozen stored fuel. 

You can bury your fuel tanks. If your tanks are made of metal or some other very durable material, and you own the tanks, consider burying them. Burying fuel storage tanks will keep the fuel warmer than leaving them exposed. Only do this with tanks you own. If you rent the tank, the lender won’t be happy with you burying them.

Boxing in your tanks is also an option. Create a wood, shed-like structure to decrease the tanks’ exposure to the elements. A physical barrier that protects it from wind, snow, and ice will keep the fuel temperature warmer.

You could also invest in a tank with climate control. These electric-powered tanks heat up fuel enough to keep the fuel in liquid form. 

When diesel fuel freezes, it prevents you from using your vehicle or machine. However, if you know what to do and be proactive, you can easily prevent this from happening. That means less equipment down time and more time being productive. If productivity is what you’re after right now, then have a look at what Municibid has to offer. Our catalog consists of vehicles, landscaping equipment, heavy equipment, and more, including some items to help keep your equipment warm this winter.