I own a BMW 3 litre diesel car. The inside of the exhaust tailpipes are as clean as a whistle, bare metal, after almost 100k miles and 11 years. On the other hand, the tailpipe of my other cars (petrol engines) have sooty deposits. In view of the recent bad publicity about diesels I sometimes feel slightly guilty about keeping it, but if I sell it someone else will get the benefit; it's a long way from scrap condition. It's also the most economical on fuel. So it's staying.