Why are diesel cars so popular in Europe?

An estimated annual 'tax gap' subsidy of some €16 billion for diesel over petrol has made Europe the world's largest market for diesel cars - but the Volkswagen scandal has put the national tax schemes supporting this industry at risk.
“There is no reason to keep subsidizing this sector," Carlos Calvo, policy analyst at Transport & Environment, told EurActiv on Monday (26 October). The efficiency of petrol-fuelled cars has improved significantly in recent years, while the diesel industry has reduced its nitrogen-oxide emissions only very slowly.

The European Commission has acknowledged that carmakers used tools to optimise their emissions test in the laboratory over the past few years, although officials argued that these techniques did not imply that the companies were using fraudulent software. However, the US Environmental Protection Agency (EPA) revealed that Volkswagen went beyond this optimisation, by installing “defeat devices” in their vehicles to cheat the laboratory tests.
Diesel vehicles produce highly dangerous nitrogen-oxide emissions, on of the most carcinogenic substances to humans.
The Organisation for Economic Cooperation and Development (OECD) pointed out last year that taxes for diesel should be higher than for petrol, bearing in mind the higher level of emissions of both carbon dioxide and harmful air pollutants than gasoline. In addition to environmental considerations, this hike would be justified in light of other social costs, the Paris-based organisation said, as diesel vehicles travel further on a litre of fuel.