When should a diesel engine air filter be changed?

Changing the diesel engine air filter when the restriction gauge indicates it is beginning to plug is the best practice. The restriction gauge provides a direct measure of the filter's condition, showing how much dirt and debris it has collected. When the restriction reaches a certain level, it indicates that airflow to the engine is being compromised, which can negatively affect engine performance, fuel efficiency, and overall longevity.

Regularly checking this gauge allows technicians to maintain engine efficiency and prevent problems associated with restricted airflow. This approach is more effective compared to changing the air filter based on a specific time frame or service intervals, which may not account for the actual operating conditions and air quality that can vary significantly from one vehicle usage to another.