Gelled Up! How To Avoid The Age-Old, Cold-Weather Diesel Catastrophe

• January 12, 2023
• Story By
  Mike McGlothlin

It’s a worst case scenario for diesel owners. It’s freezing cold outside and your truck either won’t start or (worse) starts to lose power going down the highway. You either become stranded or try to make it to your destination. Either situation usually ends with your truck requiring a tow. It’s called a gel-up and the effects are absolutely crippling. Luckily, gel-up issues can be prevented or quickly resolved if you’ve properly prepared your diesel for sub-zero degree temperatures. After recent winter storm "Elliot" blasted North America with frigid temps—giving us the coldest Christmas in years—we came across all kinds of fuel-gelling posts on social media, as well as spotted many victims parked at local shops.

Don’t let the next deep-freeze take your diesel down. Knowing why and when diesel fuel begins to gel up, performing a simple fuel filter change, running an anti-gel additive in the tank and avoiding biodiesel can all help ensure you and your workhorse don’t get sidelined in the cold. After all, winter is just getting started for those of you in the rust belt...

Take Note At 20 Degrees F And Lower

Although diesel fuel refiners include an additive package to guard against cold temperature gelling, even “winter blend” diesel has its limits in extreme cold. The tipping point varies from manufacturer to manufacturer (and blend package to blend package), but somewhere between 20 degrees F and -15 degrees F diesel fuel can reach its cloud point. Cloud point is the measure of how well diesel flows in freezing temperatures and it’s where solid wax crystals begin to form, creating a visual haze within the fuel. If left in the cloud point temperature for too long, gelling of fuel filters, water separators, fuel lines and even pumps can occur.

What Gelling Looks Like

Each winter, RCD Performance sees a host of customers facing fuel gelling scenarios, thanks in part to the company’s north-central Illinois location. When the last winter storm was forecasted (a.k.a. Elliot), the folks at RCD sounded the alarm early on in order to help everyone get ahead of it—and much of the company’s advice has made it into this article. The image above (taken by RCD Performance) illustrates what a gelled up fuel filter looks like. As you can see, very little fuel is going to pass through this filter and make it to the engine.

Change Your Fuel Filters Before The Deep-Freeze Hits

The first step in guarding against a gel-up is replacing your truck’s current fuel filter and water separator with fresh units. According to RCD Performance, it doesn’t matter what anti-gel fuel additive you add to the tank if the water separator you’ve been running is already full of water. If there is water present, you’re going to gel up. We would add that, on top of changing fuel filters before frigid temps arrive, it’s a good idea to also keep a spare fuel filter and water separator with you in the cab of your truck.

Pull Over Immediately

If your truck does begin to gel up while driving down the road, pull over at the first sign of sluggishness or lost power. Continuing to drive can have grave consequences, especially on the injection system. Today’s high-pressure common-rail fuel injection systems don’t tolerate a lack of pressure for very long before catastrophic damage is done. A wrecked late-model fuel system can run you north of $10,000 in repairs. Trust us, that $100, $200 or $400 tow bill pales in comparison to replacing a trashed high-pressure fuel pump, fuel injectors and rails.

How To Fight It: Anti-Gel Fuel Additives

A lot of diesel owners dwelling in colder climates regularly run anti-gel fuel additives during the winter as added insurance against a gel-up. This offers sound peace of mind, but when a cold-snap comes through—where temperatures dip below 0 and wind chills go lower than that—tripling and even quadrupling your normal treatment is highly advised. And, always make sure to run a reputable, proven fuel additive. That means one that makes the fuel in your tank more resistant to clouding up, disperses water without the use of alcohol (which is hard on injection systems) and preferably one that also provides a bump in cetane.

Emergency Additives

For fuel systems that’ve already gelled up, many additive manufacturers offer emergency formulas for a quick fix. For example, Amsoil’s Diesel Recovery additive dissolves the wax crystals that form when your fuel is past its cloud point, effectively liquefying gelled up diesel fuel. It can also be used to thaw out frozen fuel filters to help get you back on the road. If you use an emergency style additive that contains alcohol, one-time use is OK, but never use it unless you have to. The reason for this is that alcohol can be very corrosive inside the injection system. Luckily, Amsoil’s Diesel Recovery is alcohol-free and, while not recommended to be run year-round, repeated treatments in cold temperatures is deemed safe.

Avoid Biodiesel

Whenever possible, avoid biodiesel and biodiesel blends when arctic temps arrive. Biodiesel’s cloud point is much higher than regular number 2 winter blend diesel and it’s believed that some biodiesel blends possess a cloud point of just 40 degrees F. That’s inadequate for virtually all northern, Midwest and southeastern residents in North America. If you have no other choice than to run a biodiesel mix (many pumps dispense as high as a 20-percent blend), revert to quadruple (or better) treating with the anti-gel fuel additive of your choice.

Park Indoors

One of the best ways to avoid gel-ups is to park your diesel in a garage or shop. Obviously, this isn’t possible for everyone. In instances where you don’t have the luxury of bringing the vehicle indoors, make sure you’re utilizing the block heater, provided you have one. By warming the engine’s coolant, the engine oil, block, head(s) and engine-located fuel filter will warm up beyond ambient temp. Granted, using the block heater won’t do any favors for the fuel in the tank or the supply and return lines running to it, but it’s a better than nothing.