Diesel engines in trucks and other applications sold in the United States must meet stringent U.S. Environmental Protection Agency (EPA) emissions requirements. Many of those engines use Selective Catalytic Reduction (SCR) to meet the requirements. SCR is an emissions aftertreatment technology that converts nitrogen oxides (NOx) in the diesel-engine exhaust stream into nitrogen and water vapor, two natural components in the air we breathe.
Diesel exhaust fluid (DEF) is an essential part of the process. It is injected into the diesel exhaust stream and the heat from the exhaust, the fluid, and a catalyst convert the NOx into the harmless gases.
DEF is made from a 32.5 percent solution of technically pure urea with the rest of the mixture consisting of purified water. For the SCR unit to operate properly, the DEF must meet an exacting purity standard established by the International Organization for Standardization (ISO). This ensures that the DEF provides the purity required by diesel engine manufacturers and the quality to preserve the emissions control system and the environment.
The American Petroleum Institute (API) plays an important role in ensuring that DEF products meet the precise purity standards required. 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 vehicles with diesel engines.
Makers of DEF that have demonstrated that their products meet the performance requirements in ISO 22241 may be licensed to display the API Diesel Exhaust Fluid Certification Mark. Certification has many benefits for drivers and shops that purchase DEF. Truck drivers and fleets can find quality brands of DEF through a real-time directory which lists API-licensed products that meet diesel engine manufacturer recommendations. This ensures that diesel engine warranties are protected and helps protects the overall investment in the truck. Licensing DEF also helps support the industry’s commitment to reduce NOx emissions.
API monitors DEF quality through the Aftermarket Audit Program (AMAP) by sampling and testing certified products purchased in marketplace to make sure they meet the quality specifications and program requirements. API certification requirements are enforced through action against companies not in conformance or falsely claiming certification.
DEF can be purchased in bulk and in bottles at retail locations and via pump at select refueling locations. Be sure to look for the DEF Certification Mark from API when purchasing the product or ask your supplier for proof of certification.
