The average gap between official fuel consumption figures and actual fuel use for new cars in the EU has reached 42%, according to the latest update by the International Council on Clean Transportation (ICCT) to its on-going research into vehicle fuel consumption 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 translates into €450 per year in extra fuel costs for the average vehicle. As a result, less than half of the on-paper reductions in CO2 emissions since 2001 have been realized in practice.
The new study, jointly prepared by the ICCT and the Netherlands’ Organisation for Applied Scientific Research (TNO), describes the increasing real-world efficiency gap using systematic statistical analysis.
We analyzed data for approximately one million vehicles from seven European countries, and all data sources confirm that the gap between sales-brochure figures and the real world has reached another all time high. When we published our first study in 2013, the gap had widened over ten years from roughly 10% to around 25%. Now it has increased to 40% for private cars, and 45% for company cars.—Uwe Tietge, a researcher at ICCT Europe and lead author of the study
The analysis draws on data from 13 different sources: the user websites spritmonitor.de (Germany), honestjohn.co.uk (United Kingdom) and Fiches-Auto.fr (France); the leasing car service providers Travelcard (Netherlands), LeasePlan (Germany), Allstar (United Kingdom) and Cleaner Car Contracts (Netherlands); the car and consumer magazines AUTO BILD (Germany), auto motor sport (Germany and Sweden), WhatCar? (United Kingdom), km77.com (Spain); and the car club TCS (Switzerland).
|Divergence between real-world and manufacturers’ type-approval CO2 emission values for various real-world data sources, including average estimates for private cars, company cars, and all data sources. Source: The ICCT. Click to enlarge.|
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, said 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.
|Estimate of the reasons for the discrepancy 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 WLTP. Source: The ICCT. Click to enlarge.|
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 will be implemented in the EU from 2017 onwards.
|Type-approval CO2 emission values and the corresponding divergence from Spritmonitor.de for selected brands in 2001 and 2015. Source: The ICCT. Click to enlarge.|
The WLTP will cut the gap approximately in half but it contains new loopholes that could lead to the performance gap to increase again in the future. Further actions are therefore required, in particular on-road testing of fuel consumption and CO2 emissions under real driving conditions as well as independent surveillance testing of actual vehicles on the road.—Dr. Peter Mock