Who is correct regarding Diesel Exhaust Fluid (DEF) and its effect on vehicle performance?

The assertion made by Technician B regarding Diesel Exhaust Fluid (DEF) and its impact on vehicle performance is accurate because DEF is essential for the proper functioning of selective catalytic reduction (SCR) systems in diesel engines. These systems are designed to reduce nitrogen oxide (NOx) emissions by converting them into harmless nitrogen and water vapor. DEF is injected into the exhaust stream, where it reacts with the NOx in the presence of a catalyst to facilitate this conversion.

When DEF is used correctly, it can enhance vehicle performance by enabling the engine to operate more efficiently and produce fewer emissions. This not only helps in complying with environmental regulations but also can lead to better fuel economy, as the SCR system allows for optimized combustion processes.

In contrast, misunderstanding or misusing DEF can lead to several performance issues, such as reduced power, increased emissions, or even engine derating. Therefore, a clear understanding of DEF's role and its proper usage is crucial for the optimal performance of diesel vehicles with SCR technology.