This is really a great site...I have been reading alot! It has come to my attention that the wrong oil was put into my Benz! My car calls for Mobil 1 0w40 because of the MB 229.5 certification. And for the past 1.5 years...i have had Mobil 1 10w30 which was put in by an independent Mercedes repair shop. It really bothered me so much that the following day I immediately changed it the next day to Mobil 1 0w40. My questions are.... 1. Did it harm my car in any way for having the 10w30 oil in there? It was in there for 5500 miles for 1.5 years. 2. During the past 1.5 years...one of my oxygen sensors is failing on me. The check engine light turns off and on now. Will the wrong oil cause this? My car has 55,000 miles by the way.