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DEF Consumer Guidance

For questions about the API DEF Certification Program, contact

Using high quality Diesel Exhaust Fluid (DEF) for your diesel engine is critical to preserving the emissions control systems and maximizing the efficiency of your vehicle.

DEF (sometimes called AdBlue®) quality specifications are set by international standards organizations, and these specifications are recommended by Original Equipment Manufacturers (OEM) for use in their vehicles or equipment. However, not all DEF meets these purity standards.

To support the consumer in identifying high-quality DEF, API-certified DEF products have been verified to meet ISO/OEM purity requirements and are tested in the aftermarket to assure compliance. Through this voluntary program, these DEF marketers and their products are licensed to display the API Diesel Exhaust Fluid Certification Mark:

Maintain your fleet’s performance and minimize downtime by ensuring you procure high quality DEF for your diesel engine vehicles. Always look for the API DEF Certification Mark and search the complete list of API-licensed products in our DEF Licensee Directory.

Use of low-quality DEF in cars, trucks and other fleet vehicles can lead to damage such as catalyst poisoning, DEF injector and filter clogging, and deposit formation. Such complications could result in restricted equipment operation, costly repairs, extended downtime and even voiding of the manufacturer’s warranty.

API also provides good practice recommendations for the purchase and storage of both bulk and retail DEF.

Drivers accustomed to purchasing DEF in containers should look for the API Certification Mark as well as identify the expiration date on the bottle as the product has a limited shelf life.

When purchasing DEF at the pump, check your customer sales receipt for manufacturer and brand name information. Many states require fill up locations to share this bulk DEF information with purchasers.

Check the label on the DEF container or bottle for recommended storage temperatures. DEF can be expected to have a minimum shelf life of 12 months or even longer in optimum conditions, but a poor storage environment such as areas with average temperatures exceeding 86°F or located in direct sunlight can negatively impact DEF quality and accelerate degradation.

For bulk DEF, use dedicated storage tanks and dispensing equipment that have been thoroughly cleaned following proper protocols to avoid cross contamination. “Dirty” DEF can lead to injector clogging.

For more storage and handling tips, download our printable do’s and don’ts guide.

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