DEF stands for “Diesel Exhaust Fluid.” It’s a system that helps convert nitrogen oxide (a dangerous emission) into harmless nitrogen and water.
In 2018, the EPA required diesel particulate filters on all three-quarter-ton and larger trucks. The requirements were aimed at reducing smog, acid rain, and air pollution.
Diesel Exhaust Fluid is sprayed into the exhaust stream of diesel vehicles to break down the nitrogen oxide.
It’s important to know that DEF is not a fuel additive. It never comes in contact with diesel.
What is it, then? Diesel Exhaust Fluid is made up of 32.5% urea and 67.5% deionized water.
Urea is an organic compound also known as carbamide. It’s technically derived from one of the byproducts of urine but is synthetically made.
Deionized water is purified water with almost all of its mineral ions removed.
Together, they help reduce nitrogen oxide pollutants in exhaust gases from combustion with diesel.
On a DEF truck, the Diesel Exhaust Fluid is stored in a separate, insulated tank that typically has a blue cap. Diesel Exhaust Fluid is non-toxic and non corrosive.
There are no special measures needed to handle Diesel Exhaust Fluid, however, it can stain clothing.
A Diesel Exhaust Fluid system does require a bit more room in your truck and adds slightly to the vehicle’s overall weight.
However, DEF trucks are designed for better fuel efficiency, more optimized combustion and increased power. The EPA requires all vehicles capable of running with Diesel Exhaust Fluid do so.