like they were saying :
OK - that much is correct, when compared to a modern closed-loop managed injection system.
And there we have the big get-out clause in that line of thought. It's not the relative efficiency that's important so much as the total environmental footprint.
No 45mpg vehicle is ever going to be anywhere near as polluting in absolute terms - and they're what's important - as a vehicle using up to three times as much fuel.
In specific pollutants, a non-catted car will produce greater amounts of some emissions, but fewer of others.
In relative efficiency, a carbed car will be less efficient than one with managed closed loop injection. (and, FWIW, I'm working on fitting closed loop injection to one of my 2cv fleet at the mo. It won't be ultimately as efficient as full management, because it won't incorporate the ignition, but it'll certainly be more so than a carb.)
That, of course, is before we get into the manufacturing pollution - a modern factory may well produce less pollutants than one running fifteen years ago - but the pollution from that older car is released regardless of the production of a new car, so cancels out. We also have the raw resources used in a vehicle weighing 600kg and one weighing up to four and a half times that much.
It will always be less polluting to maintain and use an older car than to build and use a new one.
