By Russ and Tiña De Maris
Does your diesel engine require DEF (diesel exhaust fluid)? If it does, you may have heard contradictory information about DEF sources. Some diesel runners will buy only at a DEF dispenser, often at a truck stop. Others swear by “DEF in a box” from places like Walmart, and crow about the significant price break they get. Detractors warn that the label on Walmart’s DEF box doesn’t show that it meets ISO (International Organization for Standardization) standard 22241 and, hence, could be a hazard to use in a DEF vehicle. Should you play it “better safe than sorry”? Here’s the lowdown.
What is DEF? Simply put, it’s water and urea. More precisely, DEF meeting the industry-recognized standard is 32.5 percent urea, and 67.5 percent deionized water. In diesel-fired vehicles, DEF helps reduce certain exhaust emissions. Yes, your DEF should meet the stringent ISO 22241 standard. So when you swing into Wally-World and peruse the automotive aisle, you’ll soon find the SuperTech house-brand DEF next to the “gold standard” Blue-DEF. SuperTech runs nearly $5.00 less than the Blue-DEF when purchased in two-and-a-half gallon containers.
But wait! The SuperTech DEF label doesn’t show anything about meeting the ISO 22241 standard. This may cause some to shy away from saving money, and glomming onto the more expensive big label stuff. But look at SuperTech’s label a little more closely. Right on the front label, there’s the mark of the American Petroleum Institute (API), loudly proclaiming, “CERTIFIED DIESEL EXHAUST FLUID”. Here’s what the API writes about their program:
“The API Diesel Exhaust Fluid (DEF) Certification Program is a voluntary program designed to certify and monitor the quality characteristics of diesel exhaust fluid intended for use in motor vehicles with diesel engines. Diesel exhaust fluid marketers that have demonstrated that their products satisfy the requirements of the most recent and applicable edition of ISO 22241, Diesel engines – NOx reduction agent AUS 32, may be licensed to display the API Diesel Exhaust Fluid Certification Mark.”
Bottom line: Walmart doesn’t specifically spell out the ISO 22241 standard on their label, but they absolutely MUST meet that standard to get the API DEF certification. Yes, you’re safe saving money buying the “cheaper” stuff and running it in your rig.