Sep 20, 2025
3 Lessons from the diesel emission scandal
NOx emissions from diesel cars have by now approached as low levels as gasoline cars - 10 years after.
10 years ago, diesel cars emitted much more nitrogen oxides than expected. Here 3 lessons:
- Excessive diesel NOx emissions were not an issue for one manufacturer or one country only. All were implicated.
- The change to real-driving tests finally brought NOx emissions from diesel cars into line with requirements. Euro 6d-TEMP was both overdue and very successful.
- Monitoring in-use emissions is essential to enable corrective action. It needs appropriate legislation and enforcement.
For a long time, NOx emissions from new generations of Diesel cars even increased, although limit values became tighter: Chen & Borken-Kleefeld, Atmospheric Environment 88, 2014.
On the data: Plotted are average NOx emissions from new gasoline and diesel cars for every model year. The cars were measured across Europe between 2013 and 2023 by remote sensing instruments. For more information on our work Research on real-world emissions / remote sensing.
Contact: Prof. Dr. Jens Borken-Kleefeld