What Is the Shelf Life of Diesel Exhaust Fluid?

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Diesel exhaust fluid (DEF) is part of your truck’s emissions reduction system, known as selective catalytic reduction (SCR). It’s an aqueous urea solution that turns harmful nitrogen oxide into less harmful nitrogen and oxide during internal combustion. The fluid triggers a chemical reaction that reduces the toxicity of the exhaust gas, minimizing your vehicle’s effect on the environment.

Since SCR became standard in 2010, most diesel pick-up trucks rely on DEF to increase efficiency and performance. While essential, unused diesel exhaust fluid degrades over time, causing problems under the hood. Learn how long it lasts sitting on the shelf or in your tank.

Average Shelf Life of Diesel Exhaust Fluid

Diesel exhaust fluid has a maximum shelf life of 12 months when stored properly. It should be stored in a cool, dry place insulated from fluctuating temperatures, ideally between 23 and 68 degrees Fahrenheit. Extreme temperature shifts and excess heat will cause the fluid to degrade faster than usual.

If storing the DEF indoors isn’t practical, keep larger quantities on hand. The larger the storage container, the more insulated the fluid. It usually comes in one- or two-gallon jugs, 55-gallon drums or 275- or 330-gallon IBC totes. Bulk packing takes longer to heat and cool than handheld containers. The drum, jug or tote should be sealed to prevent dust, dirt and particulate matter contamination, which will damage the engine if injected by mistake.

Exposing the fluid to sunlight will decrease the urea content, making it less effective. Keep DEF indoors and in the shade whenever possible. Like unopened fluid, DEF stored in the tank is susceptible to temperature shifts and contamination. Park vehicles indoors when possible to prevent water separation.

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How Do I Know If My DEF Has Expired?

Every DEF container is demarcated by a serial number followed by an expiration date listed as DDMMYY. If the fluid is over a year old, it should be replaced.

Can I Use Diesel Exhaust Fluid If It’s Been Frozen?

Yes, you can use DEF that’s frozen as long as it has thawed. Freezing and unfreezing will not change the urea contents but will expand the fluid by up to 7%.

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Maintenance Tips for Using Diesel Exhaust Fluid

DEF quality affects engine performance. If the combustion chamber can’t break down the NOx into nitrogen and oxygen, it can clog the particulate fuel filter, the exhaust and the fuel system. When DEF mixes with diesel fuel, crystalline deposits form, leading to blockages that reduce power and increase fuel consumption.

Use these maintenance tips to protect your engine when dealing with extreme temperatures or using DEF close to the expiration date:

• Only use DEF recommended for your make/model. The chemical makeup is engineered to eliminate NOx at specific temperatures and RPM.
• Check the quality of the fluid before filling the tank to prevent internal degradation. It should be transparent or clear, viscous and free of particulates. The same should be true of the DEF in your tank. Use a dipstick to check for discoloration and leaks that cause contamination.
• Clean and replace your diesel particulate filter as buildup occurs. Drive for at least 15 minutes at a high RPM to activate the regeneration process to burn off particulates in the filter.
• Check the quality of your fuel for leaks and contamination. What color is diesel fuel?
• Don’t drive with contaminated fuel or DEF. Drain the tank and inspect related components to minimize the damage. Shop for GM kits to remove contaminated fuel.
• Monitor fuel pressure if efficiency and power decline to identify potential injection issues. Unburnt fluid passing through the fuel system will damage injection nozzles, the fuel pump and fuel filters. Replace the injection pump to get your engine back up to speed.

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Safeguarding Your DEF

DEF has become essential for many pickup trucks. Your engine won’t start without it. Store your fluid where it won’t get contaminated or degrade to make the SCR system work for your vehicle, not against it.