Originally Posted By: oil_film_movies
Seventh, thanks for the inside info. I can't find any "official" BMW statements on the internet on the issue of using 0w20 in the B58.
I feel confident in using an oil only when the BMW engineers confirm the oil film thickness is good enough. If you've seen some of the engineering studies published, you will notice that every engine design has an HTHS you must never go below. There is a sudden increase in wear when you get too low of an HTHS. That of course is different for each engine type. Stay anywhere above the minimum, and the wear rate appears to be very constant.
Those engineering studies I saw used an engine where HTHS=2.3 was the absolute minimum, and LL-14FE+ has an HTHS=2.7, so some fuel dilution margin is there.
Depends on bearing area, cam lobe area, and timing chain design where the "floor" of HTHS will be.
Pardon the delay in response, but I did confirm the 0w20 oil is okay for use in the B58. Not only is it ok, but it's what some of the cars call for on the sticker under the hood.
There doesn't seem to be any rhyme or reason for it, however after talking to some folks it seems that it's mostly on the 2017 and up F30/31/32 (non-M cars). Maybe even late production 16 cars. Possibly for fuel economy reasons?
My co worker has a 2017 F22 M240, and his sticker calls for 0w30.
I'm thinking it's exactly like the Mini B38/48 situation I mentioned, where there is no internal difference in the engines whatsoever, but they all of a sudden call for 0w20 instead of 0/5w30. Makes no sense at all to me, but it is approved for B58 long story short.
However, I was unable to locate any document that specifically states it.