The problem is that these findings do not reflect my anecdotal experience.
I have two recent measurements. About 500 km round trip and small trips inside the city.
This is accordingly about 17% and 21% increase (and it was in the same region for the older model of the same car).
Sorry, I did not include the make and model of the car because I do not want to leak too much personal information but it is nowhere close to the claimed difference.
Even more the round trip was mostly on the highway and included small city part (let say about 20 km). This differs from the official test cycle.
Also the city traffic includes high elevation differences and very bad slow traffic with constant stopping.
Also the car was more occupied in both cases (official tests consider about 70 kg driver and 7 kg luggage).
This means that in more fair test the results should be even more close to the official numbers.
So what could explain this?
I do not know as we do not see the fuel economy numbers.
Perhaps during the official tests the car is actually stationary and can not take enough air and the burning is not that efficient but a good exhaust filter hides this problem?
What is also strange is the difference between BMW 3rd series and 5th series because both use the same engines (and also some Renault models do use BMW engines but it do not know about Megane).
I calculated the fuel consumption and CO2 ratio for several models and it is about the same (as expected).
I also calculated weight to CO2 ratio for similar engines over few series and this gave also very similar results. As the different series look quite similar these days then I would assume that they also have quite similar aerodynamics.
After carefully reading again what they stating stating, it appears that even when they talk about CO2 emissions, they actually base their claims on self reported fuel consumption data from http://www.spritmonitor.de
It looks to me that the following is entered (I have not used the app) by the users.
Objective data:
Date of fuelling,
Current odometer value,
Amount and price of fuel.
Type of tires (summer/winter) [should be mostly objective]
Subjective data:
Driving style used (Moderate, Normal, Fast),
Roads driven (Motor-way, City, Country roads)
For roads driven all the options could be selected and are then doubly reported in the detailed statistics.
This means that there is no objective acceleration and speed profile and also elevation difference data is missing (is not collected).
To illustrate this I will compare two different entries for BMW 3er 320d touring efficient dynamic
The problem is that these findings do not reflect my anecdotal experience.
I have two recent measurements. About 500 km round trip and small trips inside the city.
This is accordingly about 17% and 21% increase (and it was in the same region for the older model of the same car).
Sorry, I did not include the make and model of the car because I do not want to leak too much personal information but it is nowhere close to the claimed difference.
Even more the round trip was mostly on the highway and included small city part (let say about 20 km). This differs from the official test cycle.
Also the city traffic includes high elevation differences and very bad slow traffic with constant stopping.
Also the car was more occupied in both cases (official tests consider about 70 kg driver and 7 kg luggage).
This means that in more fair test the results should be even more close to the official numbers.
So what could explain this?
I do not know as we do not see the fuel economy numbers.
Perhaps during the official tests the car is actually stationary and can not take enough air and the burning is not that efficient but a good exhaust filter hides this problem?
What is also strange is the difference between BMW 3rd series and 5th series because both use the same engines (and also some Renault models do use BMW engines but it do not know about Megane).
I calculated the fuel consumption and CO2 ratio for several models and it is about the same (as expected).
I also calculated weight to CO2 ratio for similar engines over few series and this gave also very similar results. As the different series look quite similar these days then I would assume that they also have quite similar aerodynamics.