A friend and I were bantering about urea injection for diesels. It all started when he mentioned that he was looking at a new diesel pickup and found that if it runs out of urea it will shut down. So like a couple of school boys we started wondering, can you pee in the urea tank? How about animal pee? You coast to a stop next to a farm; you ask the farmer if he has any spare cow urine? Yup the juvenile jokes just kept coming.
But urea injection for diesel engines is no joking matter. This is from Wikipedia, “Diesel Exhaust Fluid (DEF) is an aqueous urea solution used in Selective Catalytic Reduction (SCR) to lower NOx concentration in the exhaust emissions from diesel engines.”
Diesels have a lot going but low NOx (mono-nitrogen oxides) emissions is not one. NOx is caused (primarily) by high combustion temperatures. Diesels have extremely high combustion temperatures hence high NOx. NOx is a main contributor to smog and acid rain so it is important to reduce NOx in diesels.
Diesel Exhaust Fluid does not smell like pee, maybe a little like ammonia but not urine. In my opinion DEF probably won’t smell as bad as that rancid fry oil some people use in their diesels.
For more information, from far better sources, try searching urea injection on the Internet.