Originally Posted by Llamasayswhat

AdBlue is a brand/product of DEF(diesel exhaust fluid) only usable on modern diesels with a DPF(diesel particulate filter) installed. A DPF is similar to a catalyst in that it is a secondary device to further breakdown harmful emissions and pollutants and keep them out of the air. It is essentially urea(pee!) and water, and is corrosive and can burn you. It will also crystalize if left exposed to the atmosphere or spilt on anything. It's handled in its own seperate tank on cars that use it, and it gets sprayed into the exhaust system and on to the DPF to help the cleaning process