Car emissions 14% higher than advertised by manufacturers, study finds

The gap between official and real-world car emissions has grown by 80% in the past five years, despite advanced testing procedures in place to prevent such a discrepancy, a new study has found.

Carried out by the International Council for Clean Transportation (ICCT), the NGO that helped uncover the “dieselgate” scandal, the study found that when official and real-world CO2 emission values of passenger cars in Europe are compared, the figures do not align. 

The ICCT has been tracking vehicle emission disparities since the early 2010s. In 2022, a 14% gap for vehicles registered in Germany was recorded, up from 8% recorded in 2018.

“Without counteraction, official CO2 emission values will become increasingly unrepresentative of real-world values,” said Jan Dornoff, research lead at the ICCT and co-author of the report.

“This will undermine the EU’s efforts to reduce transport-related CO2 emissions and result in consumers paying more for fuel than anticipated,” Dornoff added.

The study analysed CO2 emission data reported by the European Environment Agency, along with real-world fuel consumption information from more than 160,000 combustion engine and hybrid cars as reported by consumers on the spritmonitor.de website.

Revised testing

Following the 2015 “Dieselgate scandal”, in which major automakers such as Volkswagen were found to have used so-called “defeat devices” to fraudulently lower their emissions ratings during lab tests, the methodology in place in Europe was revised.

In September 2017, the Worldwide Harmonized Light Vehicles Test Procedure (WLTP), which was agreed upon at the UN level, was instituted. The test is designed to be more representative of real driving emissions than its predecessor, the New European Driving Cycle.

However, despite the more rigorous methodology, the gap between testing and real-world emissions is again widening, according to the study.

Under WLTP, it was reported that car CO2 emissions values decreased by 7.3% between 2018 and 2022. However, the study found that real-world emissions declined by just 2.3% during the same five-year period.

Under EU law, emissions reduction targets must be achieved by manufacturers across the fleet average of vehicles produced. To ensure that the CO2 reductions are met in real terms, manufacturers should face a correction mechanism, according to Dr Peter Mock, ICCT Europe’s managing director.

This would see the EU impose revised requirements on manufacturers to improve their fleet’s average CO2 emissions performance in line with the discrepancy.

“A correction mechanism can ensure that the CO2 emissions reduction targets that manufacturers must meet in the coming years are proportionally updated in accordance with the intended original stringency written into the law,” he said.

Under 2021 EU legislation, new vehicles are required to use ​​‘On Board Fuel Consumption Monitoring’ (OBFCM) devices, which track the emissions performance of vehicles in real conditions. It is expected that this will inform CO2 monitoring from 2030, once sufficient data is collected to identify trends.

‘Not fully representative’

ACEA, a trade association representing car manufacturers, took issue with the study, arguing that the data the ICCT sourced for real-world CO2 emissions “is not fully representative” of reality.

“The only EU official source of such data is On Board Fuel Consumption Monitoring. Given that OBFCM data has only been collected since 2021, insufficient data is available to accurately describe the trends over time suggested by the ICCT,” an ACEA spokesperson told Euractiv.

The WLTP test determines CO2 values through measurements in a controlled laboratory environment, which is intended to replicate real-world driving patterns to the extent possible. The ACEA spokesperson said that the primary purpose of such lab tests is to enable customers to make comparisons between vehicles’ fuel consumption and CO2 emissions.

“It has always been fully understood that driving under a laboratory test cycle may be different to real-life driving conditions,” they said. “The actual real-world fuel efficiency experienced by drivers varies widely as it depends on many external factors such as traffic conditions, terrain, driving behaviour, road type, vehicle load, vehicle condition and weather.”

Cover photo: Under EU law, emissions reduction targets must be achieved by manufacturers across the fleet average of vehicles produced.