Last Updated on February 16, 2026
Diesel fuel behaves differently in low temperatures, affecting everything from engine performance to job schedules. The good news is that cold start diesel problems and winter breakdowns are preventable with the right knowledge and planning.
If you use diesel trucks in winter and other diesel equipment in winter, whether it’s generators or earthmovers, this guide will help. In it, you’ll learn about common winter diesel issues and get practical steps to keep your equipment running smoothly.
With proper preparation and a reliable equipment rental partner, you can manage diesel in winter and help projects stay on track without letting winter freeze your progress.
Cold Start Diesel Problems: When Does Diesel Gel?
Diesel fuel contains paraffin wax, which helps it perform efficiently in warm conditions. As temperatures drop, however, that wax crystallizes and thickens. This process is known as diesel gelling, and it can restrict fuel flow or stop it altogether.
The temperature at which wax crystals first become visible is called the cloud point. It’s the point at which the fuel goes from clear to cloudy.
The cloud point can vary, depending on the type of diesel fuel, and if it contains winter diesel additives. The cloud point of summer diesel fuel (or Number 2 fuel), for example, is approximately 14°F.
Diesel gelling is one of the main causes of cold start problems. Once diesel fuel reaches its cloud point, it can clog filters and engines may fail to start.
But winter also affects other components in diesel equipment. Batteries lose power in the cold and engine oil thickens and circulates more slowly. Together, these factors make winter one of the toughest seasons for operating diesel equipment, unless you take steps to prevent cold start diesel problems.
- Read more about winter equipment management:
Winter Diesel vs. Summer Diesel: What Number Is Winter Diesel?
There are different types of diesel fuel your equipment can use: winter diesel or summer diesel.
- Winter diesel is also known as Number 1 diesel. It is designed to withstand cold temperatures better than summer diesel.
- Summer diesel is also known as Number 2 diesel. It generally costs less than Number 1 diesel, but it is more prone to gelling in cold temperatures.
When is winter diesel available? Well, that depends on where you’re located. In the U.S. most fuel suppliers will switch to the winter blend in autumn and switch back to summer diesel in spring. You can ask your local equipment rental provider for details.
How to Keep Diesel from Gelling and Ensure Proper Diesel Equipment Operation
There are several things you can do to keep diesel fuel from gelling and avoid cold start problems that keep your equipment from running smoothly.
Pro Tips: Before taking the steps below, review all manufacturer and OSHA safety guidelines. Also wear proper personal protective equipment (PPE), like eye and skin protection. Be aware of winter weather hazards while you work.
1. Use Winter-Appropriate Fuel and Diesel Cold-Weather Additives
First, make sure you use winter diesel fuel instead of the less expensive summer blend. Unlike summer diesel, winter diesel blends are designed to handle colder temperatures.
However, using winter diesel may not be enough to keep fuel from gelling during extreme cold. Treating fuel with diesel anti-gel additives adds an extra layer of protection and helps ensure consistent performance.
You may be wondering when to use anti-gel additives. The answer is: prepare your fuel with winter diesel additives anytime the temperature is forecast to drop below freezing (32°F). Treating your fuel with the best diesel fuel anti-gel available keeps fuel flowing freely and prevent wax crystals from forming.
2. Leverage Your Engine Block Heater
Next, leverage your engine block heater. A diesel engine block heater warms critical engine components and makes cold starts far more reliable.
Plug in the diesel engine block heater at least two hours before startup. This helps reduce engine strain, improves combustion and shortens warm-up time. Using engine block heaters is a small step that can make a noticeable difference on freezing mornings.
3. Conduct Daily Winter Pre-Start Checks
Finally, don’t forget to conduct daily winter pre-start checks. Working in winter can be messy, and ice, slush and mud can take a toll on vehicles and equipment.
Simple daily checks can help prevent major issues before they begin.
- Inspect and Clean Equipment: Remove any caked-on debris and inspect the engine and other critical components.
- Drain Fuel Filters: Drain fuel filters to remove water that could freeze.
- Check and Test Batteries: Check your battery’s health and clean the terminals to maintain strong starts. Make sure the battery is fully charged. Replace worn or old batteries quickly.
- Allow Proper Warm-Up Time: Schedule work so that operators have time to allow the engine to warm up properly. How long to warm up a diesel engine in winter depends on how cold it is. In general, let all diesel engines warm up for at least 5 to 10 minutes before placing it under load.
Pro Tip: If you notice any issues or damage on your rental equipment, contact your equipment provider. They will handle the repairs or find solutions that will minimize delays to your project.
- Read more about diesel equipment management:
The Herc Rentals Advantage: Winter-Ready When You Are
Winter does not have to mean extra maintenance or unexpected downtime for your diesel equipment. Renting diesel equipment from Herc Rentals takes the guesswork out of cold-weather equipment operation.
From earthmovers and trucks to generators and climate control solutions, our fleet is professionally maintained and fully winterized before it reaches your job site, so you can focus on the work ahead. We also provide training and support to help crews operate equipment safely and efficiently in cold conditions.
Ready to tackle your winter projects without the downtime? Contact our team today, or call 1-800-432-6215, for a quote on our winter-ready diesel rental equipment.
