What is Diesel Exhaust Fluid?

Modern diesel engines require Diesel Exhaust Fluid (DEF) to operate. All newer model diesel powered vehicles are equipped with DEF tanks as per EPA standards. It is a non-hazardous solution of 32.5% urea in 67.5% de-ionized water that is injected into the exhaust stream and is never added to diesel fuel. It breaks down the nitrogen oxide into harmless water vapor and is stored in a separate, heated tank. DEF is clear, smells similar to ammonia and is used to remove harmful emissions from diesel engines. 

Why use it?

DEF is as important to the operation of any vehicle equipped with a DEF tank as the diesel fuel itself. It also contains no chemical additives. The simple chemical nature of diesel exhaust fluid is important to maintaining a functioning performance system. By using diesel exhaust fluid, a driver optimizes diesel performance while simultaneously avoids harming the environment.

In short, the vehicle will not run without it.