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Diesel Exhaust Fluid (DEF)

2010 EPA Emission Standards requires greater vehicle fuel economy and a 90% cut in nitrogen oxide (NOx) emissions.   To meet compliance, manufacturers now include a Selective Catalytic Reduction system (SCR) in most diesel engines.  The SCR combined with DEF changes diesel emissions to nitrogen, water, and carbon dioxide.


What is Diesel Exhaust Fluid (DEF)? 

DEF is a solution made up of 67.5% purified water and 32.5% urea.  DEF is non-hazardous, non-toxic, and non-flammable.  DEF is safe to handle, store, and poses no serious risk to humans, animals, equipment, or the environment when handled properly.  CARQUEST DEF products provide clear directions for proper handling.


How does DEF work?  

DEF treats exhaust gas downstream of the engine.    DEF is used as a carrying agent for the ammonia needed to reduce nitrogen oxide (NOx) emissions from diesel engines into nitrogen, water and carbon dioxide (CO2).   


What are the benefits of DEF? 

Diesel engines equipped with SCR using DEF meet 2010 EPA omissions standards.  Vehicles with SCR also benefit with higher gas mileage.

All Diesel engine manufacturers in the U.S. must comply with EPA Mandates by 2016



Contamination from non-compliant Urea, improper handling or incompatible materials are a major concern:  A 4,800 gal tanker can be contaminated with as little as one teaspoon of these materials: Aluminum, Calcium, Chromium, Copper, Iron, Magnesium, Nickel, Phosphorous, Potassium, Sodium, or Zinc.   It is imperative that DEF is stored in an approved DEF container, and only used with its own funnel.


Does DEF freeze? 

Yes!  DEF will begin to freeze at 11° F; however the SCR system is designed to provide heating for the tank and supply lines which will reduce the melting time for frozen DEF.  If the DEF freezes when the vehicle is shut down, start up and normal operation of the vehicle will not be inhibited as the SCR heating system is designed to quickly return the DEF to liquid form.

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