manager magazin: Mr. Dornoff, in your current study you examined the development of the real fuel consumption of cars and the fuel consumption stated by the manufacturers. With the result that the difference between the values has grown continuously in recent years – from 8 percent in 2018 to 14 percent in 2022. How do you explain that?
Jan Dornoff: I have to disappoint you, unfortunately the reasons cannot be determined based on the data evaluated. For our study, we analyzed the official values from the European Environment Agency and compared them with the fuel consumption data of 160,000 cars that car owners reported on the website Spritmonitor.de. Ultimately, the causes of the growing delta are also secondary. In the end, what matters is that consumption and CO₂ emissions in real operation fall just as much as the emissions stated by the manufacturers. But they don’t do that.
In order to obtain realistic values, the European Union The WLTP test procedure was introduced almost seven years ago: the fuel consumption in the car brochure should no longer be a fantasy value.
That’s right, the old test method had too many loopholes that the manufacturers exploited, from adjusted brakes to improve driving resistance to test-optimized transmission shift points.
If the consumption values now move away from reality again, the WLTP test procedure obviously does not work.
I would not go so far. The deviations are significantly smaller compared to the previous test procedure. For vehicles from 2022, the manufacturers’ official values differ from what customers use in everyday life by an average of 14 percent. In the past, the difference was sometimes more than 30 percent.
For customers, the results of their study still mean that they will have higher fuel costs than perhaps planned…
… and put more strain on the climate with your vehicle than stated by the manufacturer. And if you look at the vehicle tax, which is… Germany also depends on the CO₂ value, then a lower tax rate is applied to the vehicles than would actually be justified.
The state gets less than it deserves?
Seen that way, yes. The main problem, however, is that the EU’s desired CO₂ reduction in the transport sector is partially canceled out by an increase in the deviation. We therefore support the EU’s intention to adjust manufacturers’ CO₂ fleet values so that the delta does not continue to grow. In order to continue to achieve the target values set by the EU, manufacturers would then have to further reduce the CO₂ emissions of their fleets, for example by bringing more electric cars onto the market.
You also looked at the individual manufacturers. Who deviates particularly strongly from the stated values?
The data shows that before the switch to the WLTP test cycle, the delta between real and official values was Audi was consistently higher than average; they are now among the manufacturers with the lowest deviation. Others, such as Ford, continue to be among the companies with the largest differences. But here too we cannot analyze what the problem is based on the available data. The causes can be varied.
Curtain closed and all questions open?
With a larger database, the real fuel consumption and the deviation from the official manufacturer values could be analyzed in more detail. For example, the European Commission is creating a veritable treasure trove of real consumption data, which is determined across the EU using OBFCM devices (On-Board Fuel and Energy Consumption Monitoring Devices) in modern cars and vans.
Why didn’t you use this data for your study?
Unfortunately, these are not yet publicly accessible. They are used by the European Commission to determine the deviation and are intended to be published annually in summary form. Publishing the raw data would enable more in-depth investigations, the results of which could be used, for example, to provide consumer information on real consumption.