Quote:
Originally Posted by Thorsveinyhammer
How did you determine that the oil BMW is using is too thin?
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From this UOA of the BMW 0w30 used for 2.8k miles in a M2 CS (not really apples to apples comparing a s55 to a s58 BUT both are similar engines and the S58 theoretically will degrade an engine oil faster as compared to an engine oil in a S55)
As you can see from the UOA, the TBN is obliterated after only 2.8k miles. At 5k miles, that TBN will be close to zero, putting you at extreme risk of engine oil oxidation/sludge accumulation. The TBN on virgin BMW 0w30 is about 9. The speed of the TBN dropping in an engine oil is increased when the engine oil is too thin in high load conditions. A w40 will offer greater protection at higher temps and high load conditions and won't drop your TBN as fast as on a w30. This is why as shown on UOAs where Pennzoil Euro 5w40 is used, the TBN still looks healthy after 5k miles in a N5X/S55/S58/B58