in Europe, emissions-testing is a farce. The carmakers commission their own tests, and regulators let them indulge in all sorts of shenanigans, such as removing wing mirrors during testing, and taping up the cracks around doors and windows, to reduce drag and thus make the cars burn less fuel. Regulators also tolerate software a bit like VW’s, that spots when a car is being tested and switches the engine into “economy” mode. This is why the fuel efficiency European motorists achieve on the road is around 40% short of carmakers’ promises.
At least America’s regulators, unlike Europe’s, sometimes stage their own tests to verify the manufacturers’ findings