[Porsche-O-Phile]

I don't know about federal limits, but there most definitely is a ban on diesel vehicles in the lovely, "free" state of Kalifornia. Want to buy an efficient, clean-burning VW diesel TDi here? Nope. Can't do it. However you can go out and buy a highly INefficient PowerStroke diesel pickup or a gigantic diesel-powered commercial truck rig. Go figure. Apparently the geniuses in Sacramento think that the average citizen won't pay enough in taxes to let them have the technology in the form of a passenger car, so it's restricted to "commercial use only". The only way to get a diesel car in here is as a "brought in" vehicle from another state (which you pay out the nose to the DMV for) and it has to have I think at least 4,000 miles on it before you can do this. Needless to say, the market for older diesel Mercedes is pretty hot right now and they command a premium price here.

Idiocy at its finest.

And then you go drive around behind 1960s-vintage school busses with NO "clean-burning" technology of any sort on them puking enormous black clouds of soot. "Exempt" from testing here.

Gotta' love this state sometimes...