How To Prevent Diesel Fuel Gelling?

May 25, 2023

The Chilly Truth About Gelled Diesel

How To Prevent Diesel Fuel Gelling

Maybe you know the scenario.

Coming off an extra cold night, you find that starting your diesel engine in your vehicle or equipment for the day’s work yields only repetitive cranking coupled with an inability to fire up and turn over.

You might discover that:

· The engine starts and dies repeatedly

· The vehicle suffers from sluggish acceleration

· There is no fuel pressure

Assuming your vehicle is not making the tell-tale “click click” of a dead battery, there’s a strong possibility that subfreezing temperatures have taken a toll on your tank of diesel fuel. While those who live and work in warmer climates might enjoy fluid fuel year-round, others who navigate dramatic seasonal changes must stay vigilant about fuel treatments when temps start dropping.

So, you want to know what is diesel gelling and how to stop it? Read on to see everything about preventing diesel gelling and what to do if your fuel has gelled.

What is Fuel Gelling?

Diesel engines require high temperatures created by compression to ignite injected fuel. As you’ve likely experienced, the colder it is, the harder it is to get – and keep – the engine going.

To compound matters, diesel fuel can start to gel when temperatures drop below 32 degrees Fahrenheit.

How Diesel Fuel Gelling Happens

As the fuel gets colder, diesel will go through three stages in the gelling process:

  1. Cloud Point – Just as it sounds, when diesel hits the cloud point, it will take on a cloudy appearance. This occurs because the paraffin, or wax, in the diesel starts to stiffen and form crystals. It is still possible to drive at this point, but these changes are an indication that fuel quality is being affected. The cloud point can occur right around 32 degrees Fahrenheit or 0 degrees Celsius.
  2. Pour Point – The pour point is essentially the lowest temperature at which the diesel will still flow. The pour point could occur anywhere from 2 to 20 degrees Fahrenheit below the cloud point. Wax particles will continue to build up and increasingly hinder the diesel fuel’s ability to move through the engine.
  3. Gel Point – When the fuel remains cold for extended periods, it will gel. Typically seen at temps of 10 to 15 degrees Fahrenheit, the gel point hits when diesel freezes solid and can no longer be pumped through fuel lines. This threshold is referred to as the "cold filter plugging point." It will clog fuel lines and filters and take on a solid, gummy, wax-like appearance. Telltale signs that gelling has occurred include white smoke from the exhaust when trying to accelerate, an engine that quits running, or a dramatic change in fuel rail pressure.

What Causes Regular and Number 2 Diesel Fuel To Gel?

Diesel can gel simply because it contains wax. Paraffin wax improves fuel viscosity and lubrication and helps diesel engines produce more energy from the fuel.

However, not all fuels are created equal, and there is a wide variance of cloud and pour points depending upon the fuel’s chemical makeup, its refining process, and how it is blended.

Types of Diesel

There are four main types of diesel:

· #1 grade diesel

· #2 grade diesel

· Winterized

· Biofuel

Each of these fuels has different properties and will start to gel at different temperatures. If you want more information on what happens to fuel in the cold, read more here.

How To Prevent Gelling With The Different Diesel Types

#2 grade diesel is the most affordable, most readily available, and most widely used, performing well in higher temperatures due to its thinner consistency. But it and also DEF have a history of freezing with prolonged exposure to cold temperatures.

Winterized and Number 1 diesel fuel contains various additives that can modify wax crystal formation, and help make diesel more soluble, but these fuels are more expensive and can result in decreased lubricity and reduced fuel economy.

Biodiesels can freeze as well, but it’s important to note that their clouding and pouring points vary greatly depending on the exact fuel properties, blends, and enhancement fuel additives.

It is always prudent to know what type of fuel you are using to understand better how to optimize engine performance during cold temperatures.

Is Diesel Gelling Really My Problem?

If the temps are bitterly cold and your vehicle won't start, fuel gelling is certainly a possibility, but there could be another potential culprit.


Frozen Water vs. Frozen Diesel

Water can freeze much more easily than fuel, and it can wreak havoc by depriving your engine of fuel. If you're experiencing problems at temps ranging from 20 to 30 degrees Fahrenheit, there’s a good chance that ice is solidifying, clogging the fuel lines or filters.

Frozen water acts as any other hard particulate and can cause abrasive wear to fuel systems or prevent fuel flow by clogging fuel lines or completely blocking filters or pipes.

Visual inspection should help you quickly determine whether you are dealing with gelled diesel or ice.

Ways To Prevent Diesel Fuel Gelling

When it comes to diesel fuel and frosty weather, it’s best to power up against Old Man Winter’s grip with good old-fashioned prevention.

To avoid winter service calls, towing expenses, lost productivity, inconvenient breakdowns, and more, spend some time preparing for operating in those biting temperatures.

Because a truck, reefer, skid steer, or fleet that’s not moving is not benefiting your company’s bottom line.

Prepare your diesel engine for winter.

Here are a few tips to keep your fleet, truck, or equipment winter-ready and primed for successful operations:

· Know which diesel fuel you’re using and what its limitations are.

· Check the health of your battery.

· Utilize a climate-controlled or heated environment, when possible, to prevent susceptibility to freezing temperatures.

· Change fuel filters ahead of cold weather’s arrival.

· Explore which additives might be best for your fuel needs and vehicle situation.

· Consider using winterized fuel.

· Insulate your fuel tank, fuel filters, and fuel lines.

· Inspect your engine and change glow plugs when necessary.

· Keep an eye out for water or condensation in the engine.

With a little planning, vigilance, and extra attention to detail, you can ensure that your work vehicles and equipment remain in operation and on task.

Fuel Logic Delivers the Smart Fuel Solution To Prevent Fuel Gelling

No matter the day, hour, or season, Dallas-based Fuel Logic is on standby to keep your engines humming in whatever industry you serve.

As your trusted mobile fuel partner, we offer nationwide, no-contract service to almost any vehicle or piece of equipment on almost any site.

Whether you have a fleet of landscaping, HVAC or plumbing trucks, a construction site, generators, reefers, or a railyard, we pride ourselves on getting fuel to you fast – whenever and wherever you need it.

Beyond mobile fuel, we strive to be a comprehensive resource for all your fuel needs and to provide helpful information. We are connected to a vast network of industry professionals, and if we can’t answer a question, then we know someone else who can.

Our fuel experts are always on hand to answer your call, text, chat, or email about winter preparation for diesel – or anything else fuel-related.

Need fuel? Have a question? Got a concern? That’s what we’re here for. Contact us here!

At the end of the day, our goal is to make your life easier – one call, one gallon, one client at a time.

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