
This really bugs me.  The emissions of diesels are the cleanest of any vechicle,
but they are considered so polluting that they are banned in passenger cars
in California.  What a bunch of crap.  Diesel is the fuel of choice for 
enviromental benefit in Europe while here it's illegal for the same reason.

The particulates are nothing but carbon.  They are just an annoyance at worst.
Nothing beats the diesel cycle for efficiency and emissions, torque or engine
durability.  It's also cheaper.