Fleet Teams: How to Protect Your Diesel Systems In Cold Weather

Fleet Teams: How to Protect Your Diesel Systems In Cold Weather

Fleet Care | Fleet Maintenance | 02/08/2024
Written by Stacy Conner

You’ve just cranked the keys in the ignition. Uh-oh: the engine won’t start.

There’s nothing like trying to start a truck on a freezing cold winter morning. Whether you’ve got to make it across the state or the street, you’re not getting very far if your engine isn’t up to snuff.

Fleet teams: we’ve been there before. And we’ve got just the thing for you.

We’re Equipment Experts, Tacoma, Washington’s go-to diesel truck repair shop. For the last 20 years, we’ve been providing fleet drivers, operators, and managers with quality diesel truck repairs and advice. 

If you’re looking for ways to protect your diesel systems in cold weather, you’ve come to the right place. In this article, we’ll describe why cold weather causes problems for diesel engines and how to keep your payload moving during any cold snap.

Key article takeaways:

Why cold weather causes problems for diesel engines

A truck driving with snow-capped mountains in the distance

Before diesel fuel enters the engine, the fuel has to pass through a filter to strain out any impurities or harmful materials.

Just like someone’s personal filter can help drive what they say or do (for better or worse), the filter in your vehicle drives your engine’s success. Unfortunately, cold weather tends to damage engine filters

The No. 2 diesel fuel that’s used by your vehicle’s engine can be compromised if the engine filter isn’t in great shape. The wax inside the fuel can begin to crystallize in cold temperatures.

If this wax — called paraffin wax — crystalizes, it’s less likely to flow through the filter. The result is that the fuel filter can clog up. Reduced engine performance or total engine breakdowns can occur.


Knowing more about diesel systems in cold weather will help you keep your fleet vehicles running regardless of the season and weather.

Common diesel system problems resulting from cold weather

A person opening the hood of a semi truck

When filters clog up in the engine, several problems can occur. Common problems with diesel systems in cold weather include:

Gelling of diesel fuel

Diesel fuel gelling refers to when the wax inside diesel fuel becomes so cold that it forms particles and crystals. These particles and crystals can clog fuel filters and fuel lines.

When the particles and crystals become stuck, they form a gel-like substance that can stop the flow of fuel to the engine. As you can imagine, the loss of fuel to the engine can cause operational issues.

Fuel filter icing

All diesel fuel contains small traces of water.

When temperatures drop, the water inside the fuel can freeze. The freezing can cause ice to build up inside of the air filter. As ice builds up, the engine’s output and operation suffer.

Not taking care of fuel filters and the icing that results can spell trouble. Fuel filter icing can mean more unplanned downtime and unnecessary preventive maintenance.

Decreased fuel economy

As temperatures drop, fuel can become thicker. Thicker fuel means more friction within the engine’s components.

As more friction occurs, vehicles stand to log fewer miles per gallon. The result?

Money spent on fuel, fewer miles per gallon, and a less efficient fleet.

Winter Pro Tip

“Add bungee cords across your truck’s chains to make your semi-truck tires more secure in cold weather. Three or four bungees from one end of the chains to the other should do the trick.” – Stacy Conner, Founder and Owner of Equipment Experts, Inc.

How to keep your diesel systems working in cold weather

Close-up picture of a grill of a red semi truck

Not budgeting enough money for preventive maintenance and DOT inspections can spell trouble for a fleet. Delaying proper fleet care in cold weather can damage a fleet’s operations and reputation — not to mention customer satisfaction.

Here’s what you can do to keep your diesel systems working throughout the cold months ahead.

Try cold flow improvers (CFIs), additives, and fuel heaters

CFIs enable the paraffin wax in diesel fuel to dissolve. This special fuel additive helps break down the bonds in paraffin wax so that wax can pass through filters.

Fuel heaters can also help with cold weather problems. Fuel heaters install in the fuel delivery system, generally on diesel generator sets

These handy pieces of equipment heat the diesel fuel inside the fuel tank, fuel filter, diesel oil and water separator, and fuel delivery line. The result is smoother, more viscous oil and a healthier diesel system.

Replace No. 2 diesel fuel with No.1 fuel

You’ll also want to conduct regular maintenance checks and educate your team about proper diesel system winter care. You can do so by starting with replacing No. 2 diesel fuel with No. 1 diesel fuel and keeping your diesel systems working at peak performance.

No. 1 diesel fuel doesn’t contain paraffin wax, so it won’t gel at cold temperatures. What’s more, you’ll want to transition from No. 2 to No. 1 diesel fuel in a gradual manner.

When temperatures fall below 35° Fahrenheit, use a blend of 70% No. 2 diesel and 30% No. 1 diesel. You can also include a fuel additive as well.

As temperatures drop further, you can adjust the mixture. Blend 30% No. 2 diesel with 70% No. 1 diesel.

If temperatures drop below -30° Fahrenheit, only use No. 1 diesel fuel. Keeping tabs on your fuel during cold weather will help you keep your fleet operating at peak performance.

Practice proper winter fuel treatment and preventive maintenance

Nothing beats investing in the people around you. Training your team in the latest technologies and diesel engine care practices is your first line of defense.

Whether you’re teaching your team about preventive maintenance or fleet management, your team is one of your best assets in the fight against cold weather.

Receive winter support from diesel experts you can trust

An aerial picture of the Equipment Experts fleet team crossing their arms

Some of the most common engine issues resulting from cold weather include gelling, fuel icing, and decreased fuel economy. Fleet teams can solve these issues by addressing fuel consistency.

Fleets can nip diesel engine problems in the bud by using cold flow improvers (CFIs), fuel additives, and fuel heaters.

Managers should also run a regular preventive maintenance program and replace No. 2 diesel fuel with No. 1 diesel fuel as needed.

As our gift to you, you’re invited to learn more about proper fleet management with our fleet manager video series. These complimentary videos are designed to help you better care for your fleet.

The next time you find yourself in the clutches of cold weather, don’t hesitate to reach out to the Experts.

We look forward to providing you with warm, friendly, and helpful fleet support. Until then, stay safe and warm out there.

Frequently Asked Questions (FAQ) — And Their Helpful Answers

A picture of a snow-covered truck at sunrise

What can happen to a diesel engine in cold weather?

If left untreated, an engine’s fuel can freeze, crystalize, and plug up fuel filters and fuel heaters. As a result, the engine becomes less efficient and can break down altogether.

What can I do to take care of my diesel system in cold weather?

You can add cold filter improvers (CFIs), fuel additives, and fuel heaters to your diesel system. Replacing No. 2 diesel engine fuel with No. 1 fuel can also help keep your engine running well in cold weather.

Finally, regular preventive maintenance and training can help you better care for your diesel systems.

Where can I learn more about fleet management?

Check out the resources section on our website. For those who like words, our fleet e-book comes packed with information about better fleet care.

For those who like videos, we have a series of free 2-minute-or-less fleet manager tutorial videos you can watch any time. We’re also always available at (253) 365-6591 or sales@equipmentexpertsinc.com if you’d like to speak with a live master diesel technician.

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