Chet said:

As long as you don't mind trailing a big plume of ugly black smoke....
I guess I could paint the back of my van black and hand out masks for
the unfortunate people I might pass.

That would have been an appropriate thing to say years ago.  But since
the new series of VW/Audi direct injection TDI motors appeared back in
1992, it's completely out of touch.  For most important emissions, the
newest diesels are as clean or cleaner than spark ignition motors. 
That's part of the reason that 25% of new cars sold in England today
come equiped with optional diesels which cost more initially but are
recognized to last about twice as long and cost less per mile for
servicing even if they didn't get better fuel economy.  

Chet continued:

Also, isn't diesel fuel hard to come by in those out of the way towns I
always end up in.....

Well, if you waited until a gas motor vehicle would run completely out
of fuel from the last fill up, you'd still have plenty of driving range
to find diesel fuel.  You know of a part of the world not seviced by
diesel trucks making deliverys?  I've never known a Mecedes diesel
driver to think finding fuel was relevant "problem."