I put them on our 96' C-220 about 20K miles ago, 85K miles. Bosch offers a money back refund if your not satisfied. I was sure to have the $25.00 back in my pocket by mail in a month or so. Then I drove the car... Being an honest man there was no way I could ask for my dough back. I did get it back though because the fuel economy went up 5 to 7%, and there was a noticable improvment in acceleration. My Toyota Tundra warranty recently ran out and I put a set in the truck with similar results. I don't know if they are approved for a Merc stilll under warranty however.
Bosch spark plugs? 
Bosch 4 way plugs 
Linear Mode
