If you track your Z4M and think your bearings are fine look at this pic
Picture is of my upper rod bearings, on my 2006 Z4M with 64,000 miles (5,000 on track) running with zero issues. Oil has been always at maximum with 3,000 mile total or 4 track day intervals (Castrol TWS 10w60). Car has never been run with low oil levels or had an oil temp related limp mode, and for the past year has been run with an upgraded oil cooler. This is the only thing which saved me from a total failure. There was zero signs of trouble , i just replaced the bearings with Bimmerworlds race bearing kit as a peace of mind maintenance project. The lower bearings were much better but still had significant wear. The 5 and 6 cylinder bearings were the worst which is consistent with an oiling issue most likely due to high temp, high rpm situations on track pre oil cooler. Bearings not in order in the pic. Moral of the story is don't assume the stock bearings are in good shape! Sometimes going with your gut can save your rear.
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