Diesel Exhaust Fluid (DEF) is a non-toxic, high purity solution comprised of 32.5% urea and 67.5% de-ionized water for specific use in Selective Catalytic Reduction (SCR) systems. Using this fluid in diesel-powered vehicles, such as trucks, buses, and tractors, helps to reduce the amount of nitrogen oxides (NOx) emitted into the air by 90%. It is not a fuel additive and must be filled into the dedicated Diesel Exhaust Fluid tank on your diesel vehicle. How Diesel Exhaust Fluid Works When injected into the exhaust stream with a specialized dosing module, DEF vaporizes, leaving amonia molecules en route to the catalytic converter; once there, it converts NOx molecules into harmless nitrogen and water vapor-making for cleaner emissions. Making sure you do not run out of DEF in an SCR equipped truck is simple - watch the DEF gauge, which is part of the diesel fuel gauge, for when it is time to refill. DEF is stored in a dedicated tank next to the fuel tank on the driver's side. The tanks range in size from 6 to 23 gallons depending on the truck's application. Automotive Grade Urea Automotive Grade Urea is a special, uncoated version of highest purity. It is a main component of urea solutions like Diesel Exhaust Fluid or AUS40/45 which are used within SCR-systems for the reason of NOx reduction. It is the only type of Urea that meets the ISO 22241 specification and the only suitable Urea for the production of DEF/AUS32/ARLA32 solutions. For meeting the ISO 22241 the Urea needs to be of highest purity/quality. Specification