Re: I already consider diesel socially unacceptable
I suspect that sooty diesels are either (a) broken, or (b) have some lead-footed neanderthal at the wheel.
The big clouds of soot you see are a result of over-fuelling; this usually occurs on turbodiesels when the turbo is stalled and the driver puts his foot down - the diesel pump puts in enough fuel for the expected air mass, but the air isn't there...
More modern turbodiesels don't put in as much fuel until the pressure sensor determines that the turbo is blowing. This leads to far less smoke from the exhaust.