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ICCT/TNO study: Real-world vehicle fuel consumption discrepancy widens to 42% in Europe

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 (Germany), (United Kingdom) and (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), (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 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



Dr. Strange Love

Not surprising given the current test standards. Some folks don't mind having a stiff ride experience with the Tires over inflated.

Btw, I have stopped whining about my Wife's practice of keeping the Air Conditioning Climate setting "On All the Time". You learn to live and accept and honor your marriage vows. Besides, it is better to keep the AC compressor seals Lubricated, and the way to do this to run the compressor. So many people wonder why their system leaks refrigerant. Go Figure.


What is incredible is how long the EU has let this go on and get worse and worse. You can't really blame the car companies, it is their nature to cheat and they are all up to it (like the scorpion and the frog).
However, you can blame the EU for using the disgraced NEDC test to measure mpg and CO2/km (neither of which it was really designed for).
But now that there is a ton of taxation based on the CO2 levels, it is hard to change it and the charade goes on.
Nonetheless, they will have to do this (and probably reset the CO2 target levels while they are at it).

A lot of crow will have to be eaten, but the sooner they do it, the better.

The implication is that much of the EU's CO2 reduction program has been a fraud, but lets just get the read data and start again.

Dr. Strange Love

Mahonj. I agree. The data does not lie. The issue is with the "disgraced as you call it" NEDC test(s). It doesn't matter what is being measured.


I read it differently; what I see is the engineers can't make the ICEs clean economically. They are running out of ideas and running up against the laws of physics. The smart makers have seen the future and it ain't diesels or smaller engines or start/stop, etc. It EVs.

In the U.S. we have the answer: You vote a con man with jacked up yellow hair into office and the car makers lie to Congress about how they can't meet the specs and continue in business. So, Don the Con and the greedy Republicans relax the requirements, get paid off by the fossil fuel special interests and we set the dooms day clock ahead another decade. It happened when W. was in the White House and it will happen under Don the Con. Watch it all transpire and remember I told you so.

Account Deleted

It shows the system is corrupted by auto industry lobbyist no wander that Trump won, Brexit and more to come. People are feed up with the old system for lots of reasons.


@ mahonj:
Absolutely nothing incredible about the EU's behaviour. Several years ago, as soon as the EU started thinking a bit too loud about enhancing the pollution standards, Merkel - without being invited - arrived at their doorstep, raised her fingers in dismay and reprimanded those bad boys for even just thinking about potential actions they intended to take.
With sighs of relief, Mercedes, BMW, Audi and VW, applauded their proponent's brave action. With the stagnation of EU's intention the "car kings" adhered to their general policy and things got even worse instead of improving.
Thank (god) for Merkel.


€450 per year..
When fuel costs $7+ per gallon it adds up quickly.

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