How do you factor in the large marketplace for second-hand cars? And how about the many "classic" cars I see in my town, which would be considered junk by most economists but are desired by those with a Porsche, or Jeep, or VW, or Cadillac fetish?

I would prefer to more tightly couple the problem and the cost of the problem. If the problem is the burning of oil, then the tax should be applied to that part of the process, not the device that actually does the burning...