How Cold is Too Cold For a Diesel Truck?

Have you ever wondered how the cold weather is affecting your diesel vehicle? You have noticed that your diesel vehicle is performing differently in warm and cold weather. But how cold is too cold for a diesel truck? Why is your diesel car hard to start when it’s cold?


How Cold is Too Cold For a Diesel Truck?

How Cold is Too Cold For a Diesel Truck

How cold is too cold for a diesel truck? The diesel fuel in your fuel tank will become like gel at a temperature of 15 Fahrenheit or -9.5 Celsius and you will have trouble starting your engine. Anything below 15 Fahrenheit / -9.5 Celsius can and will cause problems for your diesel vehicle. The diesel won’t be solidly frozen, but it will not be in liquid form. You now have to rely on heating options like block heaters and glow plugs which not all diesel vehicles have.

There is a lot of speculation going on about how cold is too cold for a diesel truck. You can find information on the internet that the freezing point of the diesel fuel is around -112 Fahrenheit or -80 Celsius. Now, you think that you will never be in an area where it gets that cold and you should be good to go. Wrong.

The diesel in your fuel tank and fuel lines doesn’t have to be solid froze to cause you trouble. On temperatures below 15 Fahrenheit / – 9.5 Celsius, the diesel fuel starts to change its form and it is becoming more like a gel. Imagine a fuel in the shape of a gel getting from the fuel tank into the engine. It would be hard to travel through the fuel lines and you will have trouble starting your engine in cold winter.

Then there are the impurities in the diesel, like water. As we all know, water freezes at 32 Fahrenheit or 0 Celsius. We also know that there shouldn’t be water in our diesel fuel. But, somehow all of our diesel has a small percentage of water in it.

The diesel can get contaminated with water due to condensation and handling. The thing is that the diesel fuel tanks have no vapor pressureOpens in a new tab.

Why is My Diesel Car Hard To Start When It’s Cold?

If you know anything about how diesel engines work, you know they operate by taking in the fresh air, compressing it until it heats up, and then injecting the diesel fuel to combust and then ejecting the exhaust gases.

Because the diesel engines operate this way, there is a certain limit as to how hot the air can actually get after compression. The colder the air is, to begin with, the less hot it’s going to be after the compression occurs. In some instances, especially during winter, the air is too cold to start with that it simply cannot ignite the diesel fuel.

As a result, the diesel engines utilize glow plugs to help start the engine whenever it’s cold outside. The glow plugs act as a miniature space heater inside of the cylinder. Electricity is sent to the glow plug and it heats up the air inside so that combustion can occur. Once the engine gets to an operating temperature, the glow plugs shut off and it runs as normal.

If your glow plugs fail, it would be hard to start your vehicle. Even if your glow plugs work fine, it takes a little bit of time for them to heat up the air so you can start your engine. So, if it takes you a little bit of time to start your vehicle when it’s cold, know that the glow plugs take time to heat up the air.

How To Prepare Your Vehicle For The Winter

All vehicles perform differently in warm and cold weather. The vehicles tend to have more issues when it is cold. There are some steps that you can take to get prepare your vehicle for the cold winter.

1. Replace your fuel filter

How Cold is Too Cold For a Diesel Truck? replace your fuel filter

The most common cause of no starts and engine stalls in winter months is a clogged fuel filter. A fuel filter that is loaded with contaminants will clog and gel more easily than a fresh fuel filter. If you are already overdue for a fuel filter change, you should change it before the cold hits or you may find yourself stranded on the side of the road. A good idea is to have a backup replacement fuel filter in the trunk of your car. Local parts stores or repair shops might not have the fuel filter you need, so having one in your trunk will help you get back on the road quickly.

2. Check your car’s battery condition

How Cold is Too Cold For a Diesel Truck? check your battery

Cold weather puts huge stresses on your battery. Your engine glow plugs take a lot of amperages to heat up. Your motor oil is thicker which makes your engine harder to turn over. Most cars today have exhilarated heaters for the interior that sometimes consume over 1000 watts of power or more. Compounding the issue, batteries are less efficient when cold. You can check your battery voltage with a voltmeter or a multimeter. Some jump starters also have a feature where it tells you your battery voltage. The ideal voltage is 12.5 volts. If you have any indicators that your battery is weak, replace it because that battery will likely fail when the temperature drops.

3. Carry emergency anti-gel

There are many popular anti-gel solutions on the market, all of which can be lifesavers if the fuel in your tank gels. Anti-gels work even when the fuel in your tankOpens in a new tab.

4. Use a high-quality diesel fuel additive

Most diesel fuels in cold regions are already winterized, but poorly winterized or leftover summer-blend fuel may be still in the tanks of local diesel fuel stations. The additive will lower the gel temperature and add lubricity to protect your fuel pump.

5. Check your glow plugs

Most modern diesel vehicles will tell you when your glow plug is faulty with a check engine lightOpens in a new tab.

6. Consider a plug-in heater

Block heaters and coolant heaters can warm the engine in your carOpens in a new tab.

7. Change your tires

How Cold is Too Cold For a Diesel Truck? change your tires

Bald all-season tiresOpens in a new tab.

8. Check your tire pressure

Invest in a high-quality tire pressure gauge that can give you an accurate reading of your tire pressure. An underinflated tire will give you less traction than a properly inflated tire will on slippery or snow-covered roads. Also, as the weather gets colder, your tires will lose pressure for about one PSI every ten degrees. So, make sure that your tires are properly inflated before the cold hits. The recommended tire pressureOpens in a new tab.

9. Fix any ABS lights

A broken ABS system will hurt your ability to stop when the roads are slippery. Get any ABS fault fixed before the winter weather hits.

10. Inspect your wiper blades

If you have older wiper blades, they won’t be able to push around ice and snow as effectively as new wiper blades would. If you do replace your blades, make sure to pick either OAM or an OE level manufacturer. They would be able to survive the harshest months of winter much better than budget wiper blades would.

Igor Iwanowski

I am a certified Automotive Service Excellence (ASE) mechanic since 2018. I specialize in Brake systems, dashboard warning lights, EGRs, general engine problems, EVAP and Emissions issues.

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