Diesel Exhaust Fluid

DEF is a non-toxic, non-flammable liquid that is injected into the exhaust stream to help convert NOx into harmless tailpipe emissions. DEF is composed of purified water and 32.5% urea. DEF is readily available from the pump at many fuel stations, or it can be obtained in containers. DEF is not harmful to handle, but it can be corrosive to certain metals. DEF may be stored in sealed containers, away from direct sunlight, and in temperatures between -5° and 25° C (23° and 77° F) for up to 18 months. However, for each 5° C (9° F) increment in above this recommended temperature, shelf life is reduced by 6 months. In addition, DEF should not remain in the DEF tank of an unused vehicle for more than 6 months. DEF has a freezing point of approximately -11° C (12° F). Water should never be added to DEF. Adding water to DEF will change the DEF concentration, which will reduce SCR effectiveness. Chemicals introduced by adding unpurified water can also corrode or damage aftertreatment components or damage the DEF dosing valve. In addition, adding water to DEF will raise the freezing point. DEF concentration can be tested using a refractometer that is calibrated for DEF.