The European Court of Justice has ruled against the previous practice of switching off parts of the emission control systems in Volkswagen cars.
That's another lesson, but not just for Volkswagen.
In the past, many manufacturers had made the matter of exhaust gas cleaning a little easy for themselves.
It was clear that some mechanisms could be switched off temporarily in extreme cold, great heat or high performance.
But it was incomprehensible why the extreme cold reached up to 15 degrees for Volkswagen.
Some Volkswagens were therefore mostly on the road with partially switched off exhaust gas cleaning.
Other manufacturers have done the same, but they are not in the pillory like Volkswagen was after its fraud in California.
So far, Italian or French authorities have been sweeping all dirt under the carpet.
A ray of hope, however, is that the verdict on cars after Euro 5 is only working through the past.
Stricter Euro 6 regulations, but also technical experience with cleaning the exhaust gases from nitrogen oxide and the conversion of the engines ensure that modern diesels today can also comply with the once super-strict California regulations.