Some people really like to take simple things into an extreme.
The poor guy asked a simple question on which M.B. would serve best for his interest on the environment. I know, the 4 cylinder issue is a total misconception, but fuel economy (although an important factor on polution) is not the ONLY issue on being eco-friendly.
That is why in Europe car manufactures are now required to print the car's polution factor along with its fuel economy.
Certainly an S600 V-12 is not as green-friendly as a C180, BUT a new technology C320 V6 is certainly less poluting than an older tech 230 (W123) 4-cylinder.
Just my 2 cents...
CL 500, 1998
S 500 L, 1998
E 320 T, 1995