Question, I am finalizing the install of my new Catalytic Convertor and 2 02 Sensors on my GM car. At 110,000 the cat substrate is starting to come apart and rattle. A) Could my from day 1 use of Mobil 1 etc caused a diminshed cat life? Some posts here talk about a 20% life reduction in cats due to P content in Syn oils. B) Could the previous intake manifold leak caused coolant to infiltrate and damage a cat? C) Will the continued use of Mobil 1 TSUV, EP or German Castrol diminish** the life of the new cat? Anyway just thinking about this. IMO protecting the engine supercedes secondary "support" components like the cat-con. As one poster said, what is more important the cat or your engine internals. *lol* So,I will keep using the good stuff oil regardless.