Diesel fuel is pretty awesome, but it can be hard to handle when it gets cold. Cold weather causes diesel fuel to crystallize (gel), which makes it harder to use.

Crystallized diesel fuel can cause problems with engines. In order to avoid diesel fuel from freezing, there are a few tried and tested means of keeping your diesel from crystallizing and being rendered useless as a result.

In this article, we will fill you in on everything you need to know about diesel fuel and the temperature it freezes at.

On top of that, we will serve you with some hot tips on how best to avoid the dreaded gelled diesel.

If you’re from one of our chillier northern states like Michigan then you probably already know this as it comes with the territory up there. For everyone else, we’re here to help. 

What Temperature Does Diesel Fuel Gel?

Diesel fuel can gel as high as 20 degrees Fahrenheit. Typically it happens closer to 14-15 degrees Fahrenheit, but it is best to take anti-gelling measures when temps hit 20 degrees F.

When fuel tanks freeze, they become cloudy and hard to see. Fuel lines also become hard to work with when frozen.

Mechanics need to unfreeze the fuel before working on them.

What is Diesel Gelling?

Diesel Gelling is when diesel fuel gets cold enough that the paraffin wax in the fuel crystallizes, forming a solid inside the engine.

The process works like this:

Cloud Point

Diesel fuel is clear when liquid, but starts to turn cloudy when it gets close to cloud point.

Pour Point

Diesel engines lose their ability to flow when they reach a certain temperature.

Gel Point

Diesel engines need to be kept warm to prevent wax formation. When the diesel engine gets too cold, it can’t pump any more oil through the system.

What Causes Diesel to Gel?

Paraffin wax is typically used to make candles or other items. When heated, paraffin wax melts into liquid form. Diesel machines use paraffin wax to create heat. This creates a problem because if the temperature drops, paraffin wax forms a solid block in the engine.

Will Diesel Un-Gel on Its Own?

Yes, diesel will ungel once it warms up again.

Simply helping or allowing the diesel to warm up will melt the waxy substance and allow things to work as usual.

For example, leaving the truck in a sunny location, or towing it inside a building and letting it sit for an hour or two is likely all you will need to get things back to normal.

Cold Weather Preparation

Diesel fuels are used to power vehicles. Cold weather can cause problems when fueling a car or truck. Make sure your battery is healthy. Use a multimeter to test your battery.

If the voltage is less than 12.45 volts, then replace it. Don’t use an additive until temperatures drop below 30 degrees Fahrenheit. Plug in a block heater before temperatures reach 30 degrees Fahrenheit.

You should always check your truck before going out in the winter. Cold weather makes engines run less smoothly. Your engine may need extra help if it gets too cold.

To make sure your truck or car runs well, check it over before driving off.

What Are the Symptoms of Diesel Fuel Gelling?

There are many signs that show that the diesel has already gelled, including when you’re unable to start your car.

When the fuel rail pressure is different than what is expected, this could mean that the fuel is gelling. You’ll also notice that the fuel rail pressure spikes up as you accelerate.

How To Prevent Diesel Fuel Gelling

What Temp Does Diesel Gel

Below we have listed the best ways to avoid your vehicle’s diesel fuel from gelling.

Prevention is always the key and doing something now before it’s too late and you’re stuck on the side of the highway in sub-zero temperatures is tirelessly recommended. 

And, considering how much diesel fuel a semi truck can hold, diesel fuel gelling can be a significant issue!

Anti-Gel Diesel Fuel Conditioner

Diesel vehicles can work fine all winter long if you plan ahead by adding an anti-gel diesel conditioner. These additives are designed to prevent your fuel lines from becoming clogged up when the temperature drops.

These additives change the crystal structure of the fuel, making it easier to flow at low temperatures. You’ll pour the additive into the tank, wait about 20 minutes, then start up the car.

When using diesel additives, it’s important to follow directions carefully. You should always make sure you’re applying the right amount of product to the correct part of the engine.

This is especially true if you want to avoid damaging the engine or causing damage to other parts of the vehicle.

Basically, if you’re using anti-gel, you should use more of it to prevent freezing. You should also make sure that your engine block is heated up properly before starting your vehicle.

If your engine is running very cold, it might be too late to add anti-gel. If you’re unsure about how to heat your engine block, ask someone who knows what they’re doing.

When you are filling up, that is the best time to use your diesel fuel anti-gel. Try to remember to always add the anti-gel first when filling up.

This will help ensure that there is an even mix of the anti-gel throughout the fuel. The best time to use a diesel anti-gel is before the fuel freezes! Be prepared this winter, and pick some up before you get stuck!

Cold Flow Filters

Diesel fuel gels when exposed to cold temperatures, but extra equipment can prevent this.

Cold flow filters remove impurities from the fuel while diesel emergency filters melt the gelled paraffin and make the fuel flow again. Crystal formation causes diesel fuel to become thick and hard, making it difficult to flow.

Heated Storage 

A primary way to prevent diesel gelling is to control the temperature of the facility where your vehicle is parked. When the engine is operating, the fuel is moving and does not have an opportunity to gel.

Storing your vehicle in a heated garage or climatic-controlled structure is enough to do this.

This option may not be feasible for some people, but a simple garage lock-up may be all that is required to take the edge off the bitter outside temps. 


Diesel fuels are more expensive than regular gasoline because they contain kerosene. Kerosene is used as an additive in diesel fuel to reduce the freezing point of the fuel. This allows the fuel to flow better when cold weather hits.

Truckers add kerosene to diesel to lower the temperature of the fuel. This makes diesel more fluid and easier to handle.

Kerosene lowers the viscosity of the diesel, making it less likely to gel during cold weather. In the extreme cold zones, diesel is mixed with kerosene because it is easy to obtain there.


The North American winter is no joke. With temperatures often plummeting to well below freezing in the midst of nasty winter storms, having a reliable vehicle is essential for not just general life stuff, but also survival. 

Whether you’re new to the driving scene or a seasoned veteran of the road, every driver should have a bottle of anti-gel ready to go.

Allowing you to keep moving in bone-chilling temperatures, the importance of such a product knows no bounds. We hope very much that you found this article a useful one. 

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