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Frequently Asked Questions


  • DEF is the reactant necessary for the functionality of the SCR system. It is a carefully blended aqueous urea solution of 32.5% high purity urea and 67.5% DI water.

  • Urea is a compound of nitrogen that turns to ammonia when heated. Urea has important uses as a fertilizer and feed supplement, as well as a starting material for the manufacture of plastics and drugs. It is a colorless, crystalline substance that melts at 132.7° C (271° F) and decomposes before boiling.

  • The SCR technology treats gas exhaust downstream of the engine. Small quantities of DEF are injected into the exhaust stream and when mixed with the NOx, it changes into harmless nitrogen and water.

  • The DEF you purchase should display the American Petroleum Institute (API) certification, the International Organization for Standardization ISO 22241-1, & meet AUS – 32 specifications. This will ensure the proper purity and concentration (32.5%) of urea. Looking for more information, please go to visit

  • The production of urea involves the raw materials of ammonia and carbon dioxide. Two reactions take place in the formation of urea. The first is an exothermic (heat releasing) reaction in which ammonia + carbon dioxide creates ammonium carbamate. The second reaction is an endothermic (absorbing energy within heat) reaction in which ammonium carbamate is converted into water + urea.

  • Yes, The 32.5% urea concentration is the ideal solution as it provides the lowest freeze point. It is our understanding that all SCR systems will be calibrated to the 32.5% concentration.

  • This 32.5% solution will begin to freeze at 12 deg F (-11 deg C). At 32.5%, both the urea and water will freeze at the same rate, ensuring that as it thaws, the fluid does not become diluted, or over concentrated. Unthawing will not cause harm to the product.

  • Approximately 9 pounds per gallon.

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