I just have to brag on my 1993 300E2.8. I have had it nine years and have put 75,000 miles on it. The license plates are due and with that comes the mandatory emissions inspections. Results:

HC Max allowed 220 ppm, my car 006 ppm
CO Max allowed 1.2 %, my car 00.00 %

And this was with no special preparation, just pulled in to a random inspection station as I was driving down the street. I think it is pretty good. My lawnmower probably pollutes more (and it is electric!).