Europe is long on gasoline and short on diesel so with the same taxes diesel costs more, nowadays diesel costs a bit more in refining terms as you have to generate hydrogen to boost the hydrogen balance in the refinery and feed the hydrocracker that provides the marginal diesel. Hence the future is downsized efficient petrol engines, three cylinder turbocharged. The upcoming Euro V emission regs are also bad news for diesels. Sorry for the jargon, that's been my professional life.