Why are diesel engines subject to different emissions standards compared to gasoline engines?

Diesel engines are subject to different emissions standards compared to gasoline engines primarily because they emit different types and quantities of pollutants. Diesel combustion produces higher levels of nitrogen oxides (NOx) and particulate matter (PM) compared to gasoline engines. These emissions are of significant concern due to their impact on air quality and public health.

Because of these differences, regulatory agencies establish distinct standards to specifically address the unique challenges posed by diesel emissions. Moreover, diesel engines operate at higher compression ratios and generate more torque, resulting in distinct combustion characteristics that contribute to their different emission profiles. Thus, the regulations seek to control these specific pollutants more effectively while taking into account the operational differences between diesel and gasoline engines.