Dang, I knew I should've saved that link today. I was just reading something about that from a OEM parts specialist from NGK. He was talking about that and other things in detail about the spark plugs for BMW and MB. What I could understand was that they use a sophisticated design to make sure the plugs last 100,000miles, not 60,000 without (Pt, Ir) precious metals.. The electrode is much bigger than a platinum plug also and lasts longer, due to the design. It gets complicated explaining 3 different cooling passages to cool the plug, duh, duh, duh... Sorry, wish I could explain it better, but I kind of skimmed thru the article, b/c it was too long. Look up under your search engine either Bosch spark plugs or Bosch heat. I used those keywords, I think. The article focuses on BMW stock plugs, but it pretty much applies to MBs also.