Diesel Exhaust Fluid (DEF), also called "Aqueous Urea Solution" and in others "AdBlue," is a transparent, colorless, non-toxic, and virtually odorless liquid that is injected into the post-combustion exhaust stream of a diesel engine to reduce emissions.
- The frozen Diesel Exhaust Fluid is melted by the heat from the engine. The engine coolant that passes through the DEF tank is governed by a thermostatic coolant control valve. This alternative may take time before the selective catalytic reduction (SCR) exhaust cleaning system is fully operational
- The Diesel Exhaust Fluid has the capacity to be self-regulating not to overheat if part of the heater is outside of the liquid. It should also preferably be self-regulating to eliminate any complicated sensor and temperature regulating systems.