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Diesel Engine Care In Winter
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Tim Forestell
January 7, 2020

Diesel Engine Care In Winter and What You Can Do About It

Diesel Engines in Winter Require Extra Care

Winter weather is getting more and more unpredictable. Leaps from freezing to moderate temperatures, ice storms, polar vortexes, and random spring-like days in February have become more common in our winters. As these extremes start to flow from one to the other more often, it introduces a new set of procedures needed to maintain heavy equipment and diesel-powered machines in the winter.

2 Reasons Your Diesel Engine May Not Start In Winter

Diesel engines can start in the winter, but it can be more difficult than in other seasons. 

This difficulty comes from the very makeup of diesel fuel. The two main ways that a diesel engine can be affected by cold weather are by the crystalizing of the wax in the fuel and the addition of water to the fuel through condensation inside the fuel tank. 

In fact, starting a diesel engine at 0°F (-17°C) is 5X harder than starting one at 80°F (26°C). 

The Presence of Wax in Diesel Fuel

Wax is often found and sometimes added to diesel fuel because it is high in a property called cetane. Cetane is valuable to a diesel engine, so it’s usually a good thing that the wax is there. In cold and fluctuating temperatures, however, it can cause problems.

Diesel Wax image closeup
An example of how gelled diesel fuel can effect your engine and filters. Image borroed from Island Diesel Injection

Cetane and Diesel

Cetane is a property in diesel that contributes to easy combustion in the engine. It is a factor in any kind of diesel-powered machine, from construction and heavy equipment to trucks. The higher the cetane level is – often called the cetane number – the less delay there is from the firing of an engine to when it actually starts up. The lower the cetane level, the bigger of a lag there is from turning a key, and the machine actually starting. 

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Since diesel engines rely on compression ignition, this quicker ignition rate associated to a higher cetane level can make starting a diesel engine much easier. Further, higher levels of cetane can mean a more complete combustion, reducing the black smoke output that sometimes comes from diesel machines.  You can learn more about it in this video.

High Cetane Levels Can Make For Easier Cold Weather Ignition

Imagine what higher cetane and therefore quicker and easier ignition could mean for winter weather. Since the fuel needs to heat up enough under compression to self-ignite, cold fuel could take a while to actually ignite. Diesel that has higher cetane levels would not have to work as hard to warm up and can make starting in cold weather much easier. 

Cetane Catch-22: The Freezing of The Wax That Increases Cetane Levels

Diesel is a particularly funny fuel when it comes to winter. Although a higher cetane number can lead to more efficient engines and startups in the winter, diesel engines with higher levels of cetane often have a cetane additive. A popular source of this additional cetane is wax. Wax naturally has higher levels of cetane occurring. 

Almost all diesel contains some level of wax because of this. When added to the fuel, however, it is a liquid. But diesel has a higher freezing temperature than other forms of fuel such as gasoline. The wax can start to harden and crystallize, slowing the flow of the fuel and possibly seizing the engine. 

Why Water Forms In a Diesel Fuel Tank In Winter

As temperatures begin to fluctuate with more regularity, the issue of water forming in an equipment’s gas tank becomes more common. Water forming and mixing with diesel fuel can be more harmful to an engine than the crystallising wax. This is because water is not supposed to be found in diesel fuel while wax is more of an expected or natural product. 

The water in the fuel tank of a diesel machine can come from condensation. Condensation forms inside a gas tank when the cold fuel comes in contact with a warmer surface. When temperatures jump from freezing to moderate, the fuel takes longer to warm up than the actual tank does. So the fuel is cold – possibly with melting wax that keeps the temperature of the fuel colder for longer. It’s sloshing around the tank itself, which is warming. Water droplets form on the inside of the tank, dripping down and mixing with the diesel. 

Diesel Fuel tank in winter diagram
Visual example of how condensation can form inside a fuel storage tank. The same principal applies to fuel tanks in equipment. 
Image borrowed from Fuel and Friction.

What Happens When Water Mixes With Diesel Fuel

Water will sink below diesel, bring it to the bottom of the fuel tank and closer to the fuel pumps. The engine will pull that water into the injectors, trying to spark a combustion with water instead of fuel. An engine can sputter out, shut off, and stop working.

Other Dangers of Water in Diesel Fuel

Aside from the machine itself stopping, water can be damaging to the fuel system itself. Fuel pumps in diesel engines are very specific for the job they are made to do and have little tolerance for misuse. In fact having water in your fuel tank and being pumped through could break them pumps entirely.

Other dangers of having water in diesel fuel also include the formation of mold and fungi in the fuel tank. These micro bacteria can damage the entire fuel system, clog filters and affect the purity and function of any fuel added to the tank later on. 

Fuel Contamination Timeline
Graphic borrowed from AXI International.

Water in a fuel tank can also freeze, much like the wax. Frozen water in fuel can have the same impact as the wax, as well, and can gel inside the tank, fuel pumps and fuel lines.

A False Cold Start and Battery Drain

Both of these instances – crystalizing wax and water in the fuel tank – can lead to a sputtering and slow die of the engine. For many people, the next logical step is to turn the engine. And then to do it again. 

The same way that constantly trying to cold start an engine can drain the battery, so can trying to start an engine that simply will not start. In these two cases, however, cold starting most likely won’t make a difference: the jelling of the fuel and presence of water will make it more difficult to start.

Because of this, the continual attempt at cold starting will kill your battery. Once your battery is dead, you’re out of luck until you can get a boost, recharge it, or replace it.

Not Addressing Wintertime Diesel Challenges Is Costing You Money

In all of these cases, the equipment cannot run as is. Crystalized fuel, water in the tank, and dead batteries will do nothing but slow down your day, hold up your operators and equipment, and affect the efficiency of your job

The solution to all of these is proactive preventative action. It may seem like extra work now – an extra expense or time spent on something that isn’t a problem – but it will contribute to the health of your equipment in the long run.

Keeping your equipment and fueling cans filled, plugging equipment in, using a diesel fuel additive, strategic parking of equipment, and including battery care into daily routines can make a big difference in equipment lasting all season long. . . or not.

Five Ways To Protect Your Diesel Engine in Winter

1) Plug In a Diesel Engine in Winter To Maintain a Core Temperature

An engine block heater is a great way to keep the core temperature of your engine nice and comfortable. A warm engine can help warm fuel quicker, meaning less time spent cold starting and draining your battery. Fuel specific heaters can also help to mitigate the crystallization of wax in the fuel and any other kind of fuel gelling. 

These heaters are available with or without a thermostat, so you can either leave it plugged in and let it do it’s thing, or monitor it manually as needed with the weather. 

Either way, this simple step can help to maintain a healthy engine that will start, no matter the weather. It’s an extra step that can save you lots of time in the long run.

Block Heater Plug
Block heaters can be applied to all different engine types. Image borrowed from Camp Westfalia.

2) Keep Your Diesel Fuel Tanks Filled Up

In terms of condensation in fuel tanks, there is a simple solution for this: keep your tanks fueled up. This is especially important when those large temperature jumps are expected. A full fuel tank does not have room for condensation. 

If you have a large fleet of equipment, there are services that you can hire that can come out and fill up all your equipment for you. If you take care of all your fueling needs yourself, be sure to also fill any jerry cans you use. The same way that a fuel tank can develop condensation, jerry cans can as well. Be sure to store them in a fuel-storage area that is as temperature controlled as you can get it. 

Any large diesel fuel storage tanks on site should be double wall insulated to prevent condensation from forming. They also may have a water separator that can be checked and emptied as needed.

Diesel Fuel pouring into equipment
Image borrowed from All Data.

3) Wintertime Additives for Diesel Engine

There are a variety of different additives for diesel engines specifically made to stop the wax in diesel from gelling. These additives lower the freezing temperature so that the fuel stays fluid for colder temperatures than normal. 

There are a variety of different additives to choose from. You can find at your local garage, hardware store, or while shopping on amazon. If you’re not sure what the best kind of additive is for your diesel engine – or even if it’s a good solution for you – speak to your mechanic and get some recommendations.

4) Park Diesel Equipment Strategically

The wind blows the cold into every nook of an engine. The same way you can feel a breeze across the little sliver of your neck not covered in winter, the wind can blow right through to your engine and fuel tank. The colder your engine, the harder it is to get the equipment to start. The more times you have to attempt a cold start of your engine, the worse it is for your battery. 

Parking equipment out of the wind can be a small but powerful way to maintain a manageable engine temperature.

Snow Tractor Pushing Snow
Think about how you store your machines to help keep them working efficiently all season long. 

5) Prioritize Battery Care

Batteries, as has been explored before, can have a large impact in the winter efficiency of equipment. What makes battery care so important is that batteries themselves have water in them. If the battery dies, that water can freeze. A battery can be thawed and recharged, but it may not always work. 

Reducing the need to cold start engines and using all the tactics already explained can help keep a battery working well. Therefore, equipment can continue to start and run whenever you need it.

Use The Weather As Your Guide

Although these proactive steps can be followed all winter long, they can be especially important before changing weather or a winter storm. Many snow removal contractors depend on their equipment functioning as needed, and when needed. Checking all equipment a few hours before starting to clear snow can catch any issues and allow time to fix it. These checks include starting the engine, fueling up the tanks, checking batteries, and ensuring that equipment is all ready to be fired up when needed. 

Every day should start with a circle check. No matter where you are, what piece of equipment it is, or what the weather’s like, a circle check should be completed every day. When the cold starts and winter weather brings extreme temperature fluctuations, adding these four simple proactive steps to your winter equipment care routine will help keep your diesel engine in winter working as needed all season long.

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Tim Forestell
Tim Forestell is one of DOZR’s co-founders and CCO. Tim got started in the industry as VP Operations for Forestell Landscaping before founding DOZR with Kevin and Erin. Aside from the amazing team at DOZR, his favourite thing about DOZR are the customers. Working with DOZR renters every day gives him a peek at the evolution of different projects and hearing stories about projects being developed from start to finish.
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