Best Practices for Storing DEF

What is diesel exhaust fluid (DEF)?

Diesel exhaust fluid (DEF) is a nontoxic solution for reducing pollutants from diesel emissions. It is critical to selective catalytic reduction (SCR), which enables modern diesel engines to meet environmental commitments.

DEF is made up of about two-thirds deionized water and one-third high-purity urea. In proper concentrations, DEF can be injected into the engine’s exhaust stream to react with an SCR catalyst and nitrogen oxides in the exhaust. As a result of the reaction, harmless nitrogen and water vapor are formed.

What are the basic requirements for storing DEF?

DEF should be stored in a cool, dry, well-ventilated area away from direct sunlight. Indoors is best.

What is the shelf life of DEF?

Stored correctly, DEF generally lasts between one and two years.

What type of container should be used for DEF?

DEF is stored within a separate tank in the diesel vehicle. External DEF storage drums must meet national and international standards, including ISO 22241, American Petroleum Institute guidelines, and local safety and fire regulations. Occupational Safety and Health Administration (OSHA) standards and manufacturer guidance may also apply.

What environmental hazards can degrade DEF?

DEF can degrade in the presence of heat or sunlight, so tanks must be handled and stored appropriately. Exposure to outside air is also a factor. When purchasing DEF or receiving a shipment of it, examine the packaging closely to ensure it is in good condition.

What happens if DEF degrades or breaks down due to improper storage?

When DEF degrades, it may break down and become chemically inert. It might also develop crystals that can clog the DEF or SCR systems of the diesel vehicle. This leads to costly repairs. Always buy DEF from a trusted vendor.

How can I tell if stored DEF is still suitable for use?

To determine if stored DEF is safe to use, check these factors:

  • Expiration date: DEF packaging includes an expiration date that is valid when the DEF is stored properly.
  • Color and clarity: Fresh DEF is clear with a yellow tinge. Discolored or cloudy DEF may be unsafe.
  • Consistency: As DEF degrades, particulate matter (i.e., crystals or solid matter) may be seen around the lid or spout.
  • Smell: A slight ammonia smell is typical, but a strong odor indicates a chemical breakdown of DEF.

If you’re still unsure, or you’ll be evaluating DEF regularly, you can use a DEF tester or refractometer to get a more precise reading. If visual checks are not conclusive and you suspect a problem, it’s always best to avoid using DEF that might damage your vehicle.

What temperature should DEF be stored at?

DEF should be stored at a temperature range between 15 degrees Fahrenheit and 77 degrees Fahrenheit. DEF can withstand freezing without any performance impact, but it’s especially sensitive to heat. DEF freezes at 12 degrees Fahrenheit and can be restored through thawing. Onboard DEF tanks often include a heater to thaw the fluid.

How can I save money on DEF?

Most DEF tanks are designed to hold one gallon of DEF for every 50 gallons of diesel fuel, and one gallon lasts between 300 and 500 miles. Because large volumes are used each year, it’s crucial to look for ways to reduce your costs. One of the best ways to cut costs on DEF is to buy it in bulk. Keller-Heartt makes bulk DEF orders more affordable and convenient.

Keller-Heartt DEF products include:

Contact us to find out more or get started.


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