The roller tappets in the M3W mitigate the need for high zinc (ZDDP) oil, and the effective life of the exhaust cats is diminished with high zinc oils, if that's a concern.
I would not worry about the life of the cats. At 7 years & around 16K miles my R/H exhaust was rattling. I took it off & the cat fell out. I removed the LH & knocked the cat out. In UK there is no emission test at MOT & mine has been tested since & passed so any noise increase not a concern.
