At what temperature does diesel fuel gel? That’s a question requiring a precise answer because without adequate preparation, your diesel-powered vehicle won’t go anywhere in cold weather. Fortunately, the problem is easily avoided by using a fuel additive, which can also reverse gelling once it begins. While it’s always best to prepare your vehicle before cold weather settles in, you can avoid a breakdown by acting immediately.
At What Temperature Does Diesel Fuel Gel?
It’s right at the freezing mark, 32 degrees Fahrenheit, that the paraffin in diesel fuel begins to stiffen, leaving the fuel tank clouded. Although this change won’t prevent you from driving, it serves as a warning of how colder weather affects fuel.
Once temperatures fall between 10 and 15 degrees Fahrenheit, gelling occurs, clogging the fuel tank and fuel lines. At this point, you may have to get your vehicle towed to a garage so your mechanic can fix any ruptured fuel lines and thaw the fuel tank.
How Do You Prevent Diesel Fuel From Gelling?
You can drive a diesel vehicle, even in subzero conditions, as long as you use a fuel additive. Designed for diesel engines, a fuel additive lowers the fuel pour point (when freezing occurs) by as much as 40 degrees. It also disperses water and prevents gelling.
A diesel fuel additive works by altering the crystals that form in fuel during cold weather. Specifically, the additive reduces crystal size, which prevents diesel fuel from waxing or gelling. It changes the chemical properties of the fuel, enabling it to flow at temperatures well below zero.
An additive is also useful if the diesel has already gelled. You’ll first need to clear the tank and free the fuel line. Typically, that involves pouring the additive into the tank and allowing it to break down the gel for approximately 20 minutes before starting the vehicle, but read any instructions to make sure you follow the right steps. You may need to let your vehicle idle for a few minutes to give the fuel lines time to clear.
Cold Weather Preparation
Besides using a diesel fuel additive, there are a few other things you can do to prepare your vehicle for cold conditions. First, ensure your battery is in top condition. Following a hot summer, the battery is especially vulnerable to failure once deep cold arrives. Test your battery with a multimeter, and if the reading is below 12.45 volts, replace it. You certainly don’t want battery issues on top of fuel problems.
Second, if temperatures are far below zero, using an additive may not be enough. Remember, an additive lowers the pour point by up to 40 degrees. This means it can prevent clogging to as low as minus 30 degrees Fahrenheit. We all know colder temperatures are possible, which can render the additive ineffective. Even before temperatures get that low, using a block heater may be necessary, especially if you park outside. Get in the habit of plugging in the block heater once temperatures approach zero degrees.
With proper care of your diesel vehicle and its fuel, you can avoid being stranded on even the coldest days.
Check out all the fuel additives available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on diesel fuel, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.
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Matt Keegan has maintained his love for cars ever since his father taught him kicking tires can be one way to uncover a problem with a vehicle’s suspension system. He since moved on to learn a few things about coefficient of drag, G-forces, toe-heel shifting, and how to work the crazy infotainment system in some random weekly driver. Matt is a member of the Washington Automotive Press Association and is a contributor to various print and online media sources.