MTI: It's hard to believe that any or all anti-freeze makers would make their product so that after a certain period of time it would turn into, lets say, ACID or some other dangerous stuff. The EPA says not to discard AF into the ground as it will surely last a long time. I think the idea of changing this coolant every 2 years is just a way to get your car into the dealers service department where they will naturally find need for more work and of course more revenue. I have a 26 year old Chevy. that I rountinly change the AF every 5 to 7 years and have never had a "clogged" radiator. Of course everyone knows a Chevy is a much better auto than a MB, or am I from another planet? What say you folks who have all these terrible problems with their MB cars?