There has been much comment anyway that diesel cars in use don't match the lab test results for emissions testing. So even the latest Euro 6 /Tier X engines are worse on the open road.
For the EU test the reason is the absurd way the test cycle is conducted. Eg acceleration that is so slow - 0 - 30 mph in 20+ seconds. A 1950 car would be proud.
Also the test ambient temp is mid 20sC - yet ambient EU temp is 7C.
On the petrol side, the catalytic technology for EU was forced through by German manufacturers who had already developed it for California.
Rover in UK were going the lean burn route to reduce emissions, and their K series engine was the start. But used more fuel when catalytic tech was forced on them.
That's why I've gone back to petrol after 20 years with diesels.
