With almost 180K miles on my C280, I have never replaced the O2 sensor. That being said,you, have to realize that MB's are known for their lack of required maintenace. I suggest you try an independent shop that does foreign cars as this is an easy job. Warning, don't take it to a dealer becuse they will find many things that need attention and you will spend a lot of money with them. Also most dealers simply do not know how to work on a MB. P.S. My car runs just like it was new and it has never seen a dealer. Oh, at 100K miles I put a set of Champion Platinum plugs in even though the (OEM) plugs seemed perfect..