Europe shows why governments shouldn't tell people what vehicles and fuels to buy.
In Europe and the breakaway UK, political fondness for diesel, manifest in tax incentives, has faded.
Concern about emissions of the greenhouse gas carbon dioxide has given way to worry about oxides of nitrogen. Officials say health problems of NOx are greater than earlier thought.
Exacerbating scorn for diesel is the Volkswagen scandal. The automaker was found to have designed engines to pollute less during emission tests than on the road.
New test methods and modernization of fuels and engines might moderate the perceived disadvantages of diesel.
But political momentum against the once-favored fuel is strong.
On Apr. 4, a designer of the UK's tax incentives for diesel said, "It turns out we were wrong."
The concession came from David King, an academic who served as a top science adviser to governments led by Tony Blair and David Brown during 2000-07. In 2004, he called climate change a threat worse than terrorism.
King told a BBC interviewer that vehicle manufacturers misled the government about their abilities to mitigate NOx emissions.
On the same day King spoke, the European Parliament endorsed a rule that would elevate the roles of European Union governments in emission testing.
Automakers no longer would pay test agencies directly but would reimburse governments newly responsible for the programs.
European Commission Elzbieta Bienkowska framed the political mood when she said diesel vehicles would not vanish overnight but added, "I am quite sure they will disappear much faster than we can imagine."
Meanwhile, the mayors of Paris, Madrid, and Athens have hinted at bans on diesel vehicles.
And London Mayor Sadiq Khan has advanced by a year the start-up date of a program imposing a fee on high-polluting vehicles inside an "ultralow emission zone" in the central part of the city.
"Frankly, we don't trust the [vehicle] manufacturers," he said.
Lack of trust is the auto industry's problem.
Governmental caprice is a problem for everyone, everywhere.
