Proper purchasing, handling and storage of diesel exhaust fluid (DEF) is critical to meeting emissions standards and keeping trucks running in cooler months, says Bill O'Ryan, American Petroleum Institute's senior manager of EOLCS/DEF.
"DEF is a blend of technically pure urea and purified water, and it requires proper handling and storage to maintain its quality," O'Ryan says. "In addition, DEF is a vital part of vehicle emissions systems, and those systems should not be altered."
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O'Ryan says the quality of the DEF is just as vital as the quality of engine oils and fuels. Using an API-licensed DEF ensures it meets standards required by engine and vehicle manufacturers.
Guidelines for purchases
The API has guidelines for purchasing and storing DEF, O'Ryan says. They include: 
- Ensuring the DEF brand and manufacturer are identified. Regulations in some states require this information on receipts, but the API recommends you verify.
- Buy DEF stored away from direct sunlight in a cool, dry place.
- Inspect the packaging for signs of contamination or damage and don't buy compromised products.
- Look for the API certification mark on the bottle.
- Check the DEF's expiration date for freshness and effectiveness. If no date is visible, ask for the most recently delivered DEF products.
Guidelines for storage
Storing DEF correctly is critical to maintaining its quality, the API says. Proper storage includes:
- Don't store DEF in a truck of the area is hotter than the recommended storage temperatures. DEF stored at 86 degrees or higher will last about six months. Sunlight will also reduce shelf life.
- Store DEF in a cool, shaded area. Stored correctly, DEF can last 12 months or longer. Use the oldest DEF first.
Pouring DEF
Use dedicated equipment for pouring DEF. Don't use funnels, pitchers, hoses or other equipment used for other fluids. Clean dispensing equipment with distilled or de-ionized water, followed by a DEF rinse. Don't use tap water.
DEF in cold weather
While warmth can be a challenge for DEF, so can cold temperatures, the API says. O'Ryan says if DEF freezes in the vehicle, don't add additives to the tank to help it melt. DEF must remain pure to work correctly.
The DEF tank should have a heating element to help it thaw and keep its proper concentration. On-spec DEF is formulated to allow it thaw correctly.
