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Originally Posted by F87source
Unfortunately oil companies dont like to fund research discrediting their own products, so the best data we have is UOA done in per oil change and done extensively by the fine folks at BIOTG. Note most of them are engineers at major oil companies formulating this stuff, so clearly they know what they're talking about.
Also an engine isn't "engineered" to run an oil, the oil is engineered/formulated to meet an engines requirements. What dictates if an engine can use said oil is indeed oil passage clearance and since the b58 passes LL01 it can handle up to select 5w40 oils (low kv100 oils). So the notion that the b58 can only run 0w20 is moot, and the only reason why these cars run low viscosity FE oils are to meet the extremely stringent german emissions targets.
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As an engineer myself, the term "engineered" is relevant to marry a diverse set of requirements to a design outcome, both the oil spec and component design specs have specific goals and the engine in general would not be designed and then a specific oil created to meet it's needs. The iterative design / engineering / certification process will use and reuse relevant components.
It is not clear that the B58 does pass the use of Xw40 LL-01 oils, as the ISTA-D info in older version does show LL-01, but any BMW documentation only shows 5w30 LL-01 oils for the B58 or 0w30 LL-01FE oils (besides the recommended LL-0117FE+). So the issue maybe that it was never properly documented This SIB that just pre-dates the B58 lists LL-01 available from BMW that are only 5w30, there are no listed 0w40 or 5w40 line items:
https://www.tsbsearch.com/BMW/SI-B11-01-15
There are also revisions of the LL-01 standard, with the latest being LL-01 (2018), but finding the content seems difficult, to determine whether the current LL-01 standard actually supports anything beyond 5w30.