AdBlue

Diesel Exhaust Fluid (DEF; marketed under the name AdBlue) is a fluid used to reduce the amount of air pollution produced by diesel engines. Specifically, AdBlue is a solution of urea diluted with high-purity deionized water, with a concentration of 32.5%, and it is completely free of formaldehyde. AdBlue is consumed in the Selective Catalytic Reduction (SCR) process, which reduces the concentration of nitrogen oxides in diesel exhaust emissions.