What Temp Does Diesel Freeze?

Truck drive in winter.

The drop in the temperature during the winter season can have a devastating effect on the performance of diesel engines. The moment the diesel fuel reaches the freezing mark of 32° Fahrenheit or 0°Celcius, it elicits certain conditions for these machines to ultimately be rendered inefficient. The fuel tank becomes cloudy as the paraffin in the fuel starts its solidifying process. 

It does not immediately affect the driving capability of the diesel engine. Still, a cautionary sign that the diesel entered the zone where it is vulnerable to turn into a gel-like substance is when the temperature drops 10° to 15° Fahrenheit (-12.2°C to -9.4°C). Generally, a car exposed to these temperatures all night long cannot be driven or even get the engine to start. 

The thickening of the diesel or diesel gelling would mean the water has frozen and wax crystals are being formed, which leads to clogged filters, and eventually solidifies. A frozen fuel would mean it cannot flow any longer and ultimately becomes unusable until such time when it re-liquefies again.

Stages of Diesel Freezing & Gelling

During the winter season and in extremely cold temperatures, if a diesel-reliant motor in perfect condition does not start or stopped running, it would mean that the fuel is not flowing properly. Depending on the quality of the fuel used, the motor will start, but chances are it will not stay running for long.

1) Starts with Icing Issues

The process of diesel gelling or freezing does not happen immediately. It all starts with the water in your fuel. When you use a diesel engine, water is produced through condensation whenever the hot diesel fuel goes back to the fuel tank from the injectors. Sometimes, just by improper handling and other specific climate conditions, water can seep into the fuel tanks. The problem starts because, basically, water freezes during winter.

2) Diesel Cloud Point

In a normal environment, the paraffin in diesel fuel helps in improving its lubricity, but in a colder climate, when the temperature drops little by little, the wax crystallizes. If it reaches the diesel cloud point, those paraffin crystals would merge and becomes cloudy. The fuel does not flow smoothly, and it will start to congest in the fuel filters. 

3) Cold Filter Plugging Point

After the diesel fuel becomes unyielding, there is clogging in the fuel filter. The engine will stop running as the fuel reaches its Cold Filter Plugging Point. It would mean that the type of diesel fuel that is being used reached the lowest temperature that it can handle to achieve a trouble-free flow phase.

4) Diesel Gelling

When the temperature drops below 10°F or below -12.22°C, the diesel gelling occurs. The fuel altogether solidifies, and there is no chance for it to flow.


Common Signs of Diesel Fuel Gelling

The following are just a few common signs that the diesel fuel of your engine has entered the gelling process. However, it is important to remember that for the diesel fuel gelling to occur, it should have been exposed to a temperature lower than 10°F or -12.22°C and that the following signs are not exclusively caused by fuel gelling.

  • When you have trouble starting your engine or it does not start at all.
  • The engine will start but will not run for long.
  • There is difficulty in accelerating.
  • No fuel pressure at all or actual pressure remains low while the desired pressure goes up.

Ways to Prevent Diesel Gelling

Diesel gelling is a normal occurrence for those people living in extremely cold places, but it does not mean they can no longer drive a vehicle using diesel fuel. There are ways to prevent this problem from happening.

Be prepared for Winter Season or Colder Climate

It never hurts to ensure that your engine is in top condition. Make the necessary trip to the auto shop and let a certified mechanic do the regular checkup on your battery. Batteries are susceptible to fail once the temperature drops lower than the usual. Have your mechanic do the multimeter testing to see if it is below 12.45 volts and if it is, battery replacement is necessary. Clean up the battery cables to get a good connection. Also, it is best to test the alternator too, as they do not last forever.

Use Fuel Additives To Prevent Clogging

Due to the necessary changes in diesel fuel production to make it more environment-friendly, it has become vulnerable to gelling. To deal with this problem, certain fuel additives are needed to ensure that the wax crystals would not altogether solidify. Its presence in the diesel fuel will help in removing water; thereby, no icing will occur. More importantly, the additive will enable the diesel to flow freely, even at subzero conditions. It lowers the pour point of the diesel fuel up to 40 degrees. The pour point refers to the lowest temperature that the diesel fuel can flow when it is cooled.

Use the Block Heater

Not all diesel engine owners are aware that they have a block heater in the vehicle, and therefore, they don’t use it during the winter season. However, if your vehicle is not equipped with one, make sure to invest in a block heater as it would make your life easier. If you found it, have it tested to ensure that it’s working fine. A multimeter can easily check its efficiency. When the temperature starts to drop, plug it in before it reaches zero degrees. This simple habit will lessen the chances of diesel gelling if the additive finds it too hard or is not enough to prevent it from happening due to the continuous drop in temperature.


Things to Do When Diesel Gelling Occurs

Most of the old folks would tell you that prevention is the cure, but if the problem has already occurred, it is wise to know what your options are to avoid getting stranded in a cold environment and just wait for the cavalry to arrive.

  • If possible, take your vehicle somewhere safe and warm, preferably inside a building. This will help in relaxing the diesel fuel and let it warm up. 
  • Get your gloves and inspect your fuel tanks. This is important as bacteria can grow in diesel fuel, and you don’t want to get the diesel bug by being careless.
  • Look into the fuel filter if there are signs of diesel gelling such as the presence of wax particles. Remove the water from the water separators and change the fuel filter if it is clogged.
  • Use an emergency De-Gel solution such as Power Service Diesel 9-1-1 to liquefy the gelled diesel fuel. It is not recommended to use it regularly but only during emergencies. Read the instructions carefully and follow each step properly.

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