How to Maintain DEF Quality

API guidelines help fleets ensure that diesel exhaust fluid meets high standards.
Originally published on Construction Equipment.

America Petroleum Institute licensed DEF ensures that it meets the high standards required by engine and vehicle manufacturers.

Diesel exhaust fluid (DEF) is a critical component in achieving both optimal performance and compliance with emissions standards. To maximize the benefits of DEF, it’s essential to understand proper purchasing, handling, and storage practices.

Diesel exhaust fluid (DEF) is a blend of technically pure urea and purified water, and it requires proper handling and storage to maintain its quality. In addition, DEF is a vital part of vehicle emissions systems, and those systems should not be altered.

The quality of the DEF is as vital as the quality of the engine oils or fuels. Using America Petroleum Institute (API) licensed DEF ensures that it meets the high standards required by engine and vehicle manufacturers.

API guidelines for DEF

Purchasing DEF

Several factors ensure a high-quality product.

• Buy DEF stored away from direct sunlight in a cool, dry place.
• Inspect the packaging for signs of contamination or damage. Avoid purchasing compromised products.
• Look for the API certification mark on the bottle.
• Check the expiration date to ensure freshness and effectiveness. If no date is visible, request the most recently delivered DEF products.

Storing DEF

Proper storage of DEF is crucial to maintain its quality.

• In-vehicle storage: Avoid storing DEF in a truck if the area is hotter than the recommended storage temperatures. DEF stored at 86 F or higher will last about six months. Sunlight exposure also reduces its shelf life.
• Shop storage: Store DEF in a cool, shaded area. Properly stored DEF can last 12 months or longer. Use the oldest DEF first to avoid expired products.

Pouring DEF

• Use dedicated equipment for dispensing. Avoid using funnels, pitchers, or hoses used for other fluids.
• Clean dispensing equipment with distilled or de-ionized water, followed by a DEF rinse. Do not use tap water for cleaning.

Diesel exhaust fluid (DEF) is a critical component in achieving both optimal performance and compliance with emissions standards.

Cold weather usage of DEF

Handling and storing DEF can be challenging in wintertime. Like water, DEF will expand up to 7% when frozen and can damage a storage tank if it is full or nearly full when it freezes. Keep the tank less than full to eliminate this risk.

Others consideration include:

• If DEF freezes in the vehicle, do not add additives to the tank to help it melt. DEF needs to remain pure for it to work correctly.
• In cold weather, the vehicle will generally start without an issue, and the DEF tank has a heating element that can quickly thaw the DEF. Don’t worry; on-spec DEF is specifically formulated to allow the fluid to thaw at the proper concentration.

API’s recently launched DEF Consumer Guidance resource page offers clear guidance to drivers, fleet managers, and others to ensure optimal performance and compliance with emissions standards. A downloadable Do’s and Don’ts Guide for DEF storage is also available as a resource.