Press release

Real-world vehicle fuel economy gap continues to widen in Europe

Latest study shows average discrepancy between passenger vehicle type-approval test results and in-use fuel consumption and greenhouse gas emissions now at 40 per cent in the EU

The gap between official fuel-economy figures and the real world for new cars in the EU has reached 40 per cent, according to the latest update by the International Council on Clean Transportation (ICCT) to its on-going research into in-use vehicle fuel efficiency and CO2 emissions.

Since 2001, the discrepancy between official measurements of vehicle efficiency and actual performance of new cars in everyday driving has more than quadrupled—a discrepancy that now translates into €450 per year in extra fuel costs for the average vehicle.

The updated study arrives hard on the heels of revelations that a similar gap in nitrogen oxide (NOx) emissions from diesel passenger vehicles was, at least in the case of Volkswagen, deliberately engineered, and as the European Commission prepares to adopt an improved test procedure that would produce more realistic vehicle test results.

The new study, jointly prepared by the ICCT, the Netherlands’ Organisation for Applied Scientific Research (TNO), and Germany’s Institut für Energie- und Umweltforschung Heidelberg (IFEU), describes the increasing real-world efficiency gap using systematic statistical analysis.

“We analyzed data for more than half a million vehicles from six European countries, and all data sources confirm that the gap between sales-brochure figures and the real world has reached an all time high,” said Uwe Tietge, a researcher at ICCT Europe and lead author of the study. “When we published our first study in 2013, the gap had widened over ten years from roughly 10 per cent to around 25 per cent. Now it has increased to 36 per cent for private cars, and 45 per cent for company cars.”

The analysis draws on data from a number of different sources: the user websites (Germany) and (United Kingdom), the leasing companies Travelcard (Netherlands) and LeasePlan (Germany), the car and consumer magazines AUTO BILD (Germany), auto motor sport (Germany and Sweden), WhatCar? (United Kingdom), (Spain) and the car club TCS (Switzerland).

The researchers assessed in detail the underlying reasons for the growing divergence. “About three quarters of the gap between laboratory test results and real-world driving is explained by vehicle manufacturers exploiting loopholes in the current regulation,” summarizes Dr. Peter Mock, Managing Director of ICCT Europe. For example, manufacturers can decide to specially prepare the vehicle’s tires for testing or to fully recharge the vehicle’s battery before testing—measures that are not forbidden by regulation, but at the same time are not representative of real-world driving. Another quarter of the gap is explained by the deployment of technologies that have a greater effect on fuel consumption during laboratory testing than under real-world driving conditions, such as stop-start technology, and by ensuring that options that tend to increase fuel consumption—such as running the vehicle’s air conditioning— are turned off during laboratory testing.

Manufacturers measure vehicle fuel consumption in a controlled laboratory environment, using a test procedure called the New European Driving Cycle (NEDC). This procedure was developed in the 1980s and was not originally intended to be used for fuel consumption testing. A new and more appropriate test procedure, the Worldwide Harmonized Light Vehicles Test Procedure (WLTP), has been developed through the United Nations and is ready for implementation in the EU as early as 2017.

“Without introduction of the new test procedure, the WLTP, we expect that the gap will grow to about 50 per cent by 2020. The WLTP would cut the gap approximately in half, and should therefore be introduced in the EU by 2017,” concludes Dr. Mock. But the ICCT researchers warn that the WLTP will not resolve all open issues, and could itself inadvertently contain new loopholes that could lead to the performance gap to increase again in the future. Further actions are therefore required, in particular compliance testing of randomly selected production vehicles.   From laboratory to road – A 2015 update of official and “real-world” fuel consumption and CO2 values for passenger cars in Europe

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Contact: Peter Mock, +49 (30) 847129-102,


Divergence between real-world and manufacturers’ type-approval CO2 emissions for various real-world data sources, including average estimates for private cars, company cars, and all data sources.

Estimate of the reasons for the divergence between type-approval and real-world CO2 emission levels for new passenger cars in the past as well as in the future, with and without introduction of the new WLTP test procedure.

Full list of contacts

Institut für Energie- und Umweltforschung Heidelberg (IFEU)
Mr. Udo Lambrecht
+49 (6221) 4767 35

Netherlands’ Organisation for Applied Scientific Research (TNO)
Dr. Norbert Ligterink
+31 (0) 888 668 058

The European Consumer Organisation (BEUC)
Ms. Chris Carroll
+32 (0) 2 789 2754

Federation International de l’Automobile (FIA)
Ms. Laurianne Krid
+32 (0) 2 282 0818

European Automobile Manufacturers Association (ACEA)
Mr. Petr Dolejsi
+32 2 738 7357

Transport Environment
Mr. Greg Archer
+32 2 893 0849

European Commission, Enterprise Directorate-General – Automotive Industries
Mr. Klaus Steininger
+32 2 296 9637