Abstract:

This paper examines the gap between official and real-world tailpipe carbon dioxide (CO₂) emission values of European passenger cars registered since the introduction of the Worldwide harmonized Light vehicles Test Procedure (WLTP) in 2017. This study finds that the gap between real-world and official CO₂ emissions of new cars continues to widen, most notably for plug-in hybrid electric vehicles (PHEVs).

The report is the first ICCT analysis to assess the gap using on-board fuel consumption meter (OBFCM) data submitted to the European Environment Agency for approximately 8 million cars newly registered between 2021 and 2023, the most recent data available. While earlier ICCT studies focused on internal combustion engine vehicles, including hybrid electric vehicles and mild-hybrid electric vehicles, the OBFCM dataset enables analysis of PHEVs as well. The results are compared with user-reported fuel consumption data from the German website Spritmonitor.de, covering vehicles registered between 2001 and 2024.