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YEven though it part of a technology invented in the 1950s, diesel exhaust fluid is relatively new within the automotive space. It was introduced due to pressure from environmental activists and government authorities.



What Is Diesel Exhaust Fluid?

Diesel exhaust fluid is a solution designed to break down nitrogen oxide emissions typically created as part of the combustion process in diesel vehicles. It is composed of deionized water and urea and is sprayed into the exhaust gases of the vehicle to turn the nitrogen oxides into separate parts of water and nitrogen.

How Does Diesel Exhaust Fluid Work?

The process used to break down NOx emissions is called “selective catalytic reduction” and requires a supply of ammonia gas within a urea solution. Special injectors convert the ammonia in a catalyst, which in turn breaks down the emissions. The fluid is kept in a separate tank (which usually has a blue cap for identification purposes) and does not come into contact with the diesel fuel itself. A vehicle will consume diesel exhaust fluid at a specific “dosing rate,” which is calculated as a ratio of the diesel fuel used. This fluid is a critical component and is heavily regulated by the U.S. Environmental Protection Agency.

How Is Diesel Exhaust Fluid Made?

The crucial component in diesel exhaust fluid is urea. The urea is mixed with deionized water to create the fluid used in the automotive industry.

How Does Diesel Exhaust Fluid Fail?

  • It may become contaminated.
  • It may deteriorate if exposed to excess heat for sustained periods.

What Are the Symptoms of Failure?

  • “Fluid Quality Poor” message will appear.
  • Vehicle performance may be impeded.

What Are the Implications of Failure?

  • Vehicle use may be restricted by on-board regulators until the issue is fixed.

The use of selective catalytic reduction technology in diesel exhaust fluid has allowed vehicle manufacturers to adjust and tune engines in later models, thereby increasing torque and improving fuel efficiency.

If you have questions or concerns about diesel exhaust fluid or any of your vehicle’s components or fluids, come into your local pep boys local Pep Boys where we can answer any question, help you find any part, or perform any vehicle service you might need.