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About DEF

What is Diesel Exhaust Fluid?

Diesel Exhaust Fluid (DEF) has emerged as the leading method to control diesel engine NOx emissions, a pollutant that damages our health and the environment by contributing to acid rain and the formation of smog. Since 2010, federal regulations under the Clean Air Act have set strict limits on emissions for new diesel vehicles.

DEF is a high-purity solution of 32.5% automotive grade urea and 67.5% pure de-ionized water that works with Selective Catalytic Reduction (SCR) emission-reducing technology to reduce NOx emissions. DEF is an odorless, colorless, non-flammable and nontoxic solution that is harmless to people, equipment and the environment.

DEF is injected into the exhaust system of SCR-equipped diesel engines and breaks down NOx molecules into harmless nitrogen and water.


Click here to learn more about DEF Storage and Quality

Click here to learn about MacEwen DEF certification by the American Petroleum Institute