It's not just trucks - I was able to get my (pre-cheating-scandal) 2003 VW TDI to belch a cloud of smoke if I idled for a while (over five minutes) then worked

It's not just trucks - I was able to get my (pre-cheating-scandal) 2003 VW TDI to belch a cloud of smoke if I idled for a while (over five minutes) then worked it hard (e.g. a freeway onramp). I remember getting honked at by a Prius once... IMO, these occasional particulate emissions were outweighed by the excellent fuel economy - rated at 46 MPG but regularly 43 MPG. Of course, this technology has been largely obsoleted by electric drivetrains. No rolling coal from a Tesla!