They are just learning about this over in Europe. The advertised European emissions and fuel economy numbers for automobiles are way way better than what the cars get on the road. Economist article goes on and on about how the car makers cheat, including programming the automobile microprocessors to recognize the start of an emissions test and switch over to an ultra clean mode for the duration of the test. The Economist writers seen surprised to find a gap between "objective" testing and real world driving.
Over here we figured this out years ago. Your Mileage May Vary has been a cliche for a long long time. It seems to take the Euros longer to catch on.