I was speaking of carbon monoxide. The carbon dioxide emissions go up as the efficiency of the engine increases, because CO2 is the result of perfect combustion. As well it's not a toxin regardless of what the idiot Al Gore or the EPA says. And of course if four people travel in the car they make as much CO2 as the car. CO is a deadly toxin and the result of imperfect combustion. So it makes sense that the newer car emits a bit more CO2. Not a problem.
Recycling of old cars is quite a science in itself, and can be done very efficiently and with little pollution. It's how the Japanese and Koreans do it as they have little in the way of iron ore.