Diesel Exhaust Fluid (DEF), also known as AUS 32 (Aqueous Urea Solution 32%, marketed as AdBlue®) or AUS 40 (Aqueous Urea Solution 40%), is a solution that helps reduce harmful emissions from diesel engines.
DEF is injected into the exhaust system equipped with Selective Catalytic Reduction (SCR) technology. In the SCR system, the DEF reacts with nitrogen oxide (NOx) emissions, converting them into harmless water vapor and nitrogen gas.
The majority of DEF in Australia is used in trucks, large passenger buses, diesel passenger vehicles, train locomotives, some agricultural, mining, other off-road equipment and marines.