Which model year did inclusion of EGR systems become mandatory if the vehicle was factory equipped?

The requirement for inclusion of Exhaust Gas Recirculation (EGR) systems became mandatory for vehicles that were factory equipped starting with the 1990 model year. This regulation was part of the broader effort to reduce emissions and improve air quality by recirculating a portion of the engine’s exhaust back into the combustion chamber, which helps lower nitrogen oxide emissions.

From 1975 to the late 1980s, EGR systems were used in some vehicles but were not universally mandated, as different manufacturers implemented various emission control technologies based on compliance with regulations that evolved over the years. The changes in the early 1990s represented a significant shift in emission control standards, reflecting a more rigorous approach to addressing air pollution.

Requiring EGR systems from the 1990 model year onward ensures that newly manufactured vehicles incorporate technology designed to minimize harmful emissions right from the start, thus aligning with the federal environmental regulations that took effect during that period. Understanding this timeline is critical for recognizing the evolution of emissions standards and their impact on vehicle design.