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What Happens When DEF Freezes? Four Problems and Solutions

  • Post published:December 19, 2023

DEF is required in most diesel vehicles to reduce NOx emissions and improve engine fuel efficiency and performance. Made of deionized water and automotive grade urea (typically 67.5% and 32.5%), it’s injected into the exhaust stream to react with emissions to reduce the toxicity of the product coming from the tailpipe.

Diesel exhaust fluid is likely low on your list, but it’s still a purchase we want to help you protect. One time to consider extra protection is during extremely cold weather.

Does DEF freeze?

Yes, diesel exhaust fluid (DEF) can freeze at 12 degrees Fahrenheit. Prolonged 12 degrees days isn’t common here in the Pacific Northwest, but our friends in Eastern Washington and Idaho may appreciate knowing that if DEF does freeze, the product is perfectly safe to use once thawed. The water in DEF does not separate when it freezes, so its physical and chemical properties are maintained.

What are the risks of frozen DEF?

While frozen DEF is safe to use in your vehicle and equipment, you may not want to lose time waiting for a block of ice to melt before you can pour it into your tank, or risk losing product from a damaged storage container. Here’s the tips on using DEF in the winter that your mechanic wants you to know.

Problem: My DEF froze and now my storage tank is cracked or damaged.

Solution: DEF can expand up to 7% when frozen, so keep tanks less than full in cold temps. This includes any smaller containers you may transfer from your bulk DEF container. You may notice that your Christensen bulk DEF deliveries are not completely full to ensure you don’t experience container damage or loss of product (we’re big on safety). If your Christensen DEF tote rental is damaged, or you need a new bulk DEF container, please call us. We’d be happy to keep you safe, sane, and saving product.

Problem: The DEF in my bulk storage container froze and now I have to wait for it to thaw.

Solution: Unfortunately, a frozen DEF tote is a waiting game. Never add products to prevent the DEF from freezing or to lower the freezing point. DEF is water and urea and must remain pure for it to work correctly. 

Your best course of action is prevention. Winterize your DEF supply by keeping snow off and away from your storage unit and keep the container off the ground. If you rent one of our 330-gallon DEF totes, they come with a built-in ground spacer! If you’re in area prone to wind chills, consider throwing up a plywood wind barrier around your DEF storage.

Problem: The DEF fluid in the bulk container doesn’t appear frozen but I’m unable to dispense.

Solution: Leftover product has probably frozen inside the hose. Simply detach the hose and place it in warmer temperatures to thaw. Once thawed, reattach continue business as usual.

Problem: The DEF inside my vehicle is frozen.

Solution: It is okay if DEF freezes inside your tank. Let the product thaw and do not add any additional products. The heating element in the DEF tank will thaw the DEF while the engine runs. It is specifically formulated to allow fluid to thaw at the proper concentration. If you have a new vehicle, the frozen DEF may result in a fluid level sensor that won’t let you run the engine. In this case, you’ll need to wait for it to thaw or call your mechanic. If parking outdoors in freezing temps is your only option, you might ask them about wrapping the tank in a thick textile padding to keep frost at bay. It’s like an ugly Christmas sweater…but for your DEF tank.

When does DEF expire?

This last one isn’t specific to winter, but we like helping our customers plan their product refills so they’re never overloaded on products or in a situation that slows operations.

Diesel exhaust fluid (DEF) has a shelf life of 12 months in optimal conditions. If you’re storing extra product, make sure it’s in HDPE plastic containers (all your Christensen containers are safe) or stainless steel. DEF is slightly corrosive and may corrode other types of metals, resulting in contamination and something you no longer want in your machines. If your product is nearing that 12-month mark, give us a call before you’re torn between using the expired product or halting operations.

Keep moving with Christensen

Need bulk DEF delivered? Need more DEF jugs delivered? Easy. Call us at 1.855.335.9448 or use the form below to request the product today.

Christensen is a local service provider. We deliver fuels, lubricants, and propane to local businesses that want reliable deliveries, streamlined processes, easy product management, and a partnership with an expert who is dedicated to keeping you moving. With locations in WA, OR, ID, and AZ, we have local Account Managers ready to serve your individual location, and a broader team to streamline your company’s needs at multiple locations.