Caterpillar - 3996151

What is Diesel Exhaust Fluid (DEF)?

Diesel Exhaust Fluid (also known as AUS 32 and commonly referred to as AdBlue in Europe, Australia, and New Zealand) is a solution of solid urea dissolved in deionized water to produce a concentration that is 32.5% urea and 67.5% deionized water.
How DEF Works

Controlled amounts of the DEF solution are injected into the engine exhaust stream prior to the SCR catalyst. The temperature of the exhaust converts the urea in the DEF to ammonia. The ammonia and NOx in diesel exhaust react in the presence of the SCR catalyst to convert the NOx into nitrogen (N2) and water (H2O).