Just my two cents. Assuming the cooling works the same in the Grenadier as in BMW's implementation, the oil temps are held up at about 240F in normal operation, but when temperatures get high, they actually drop to about 210F as BMW seems to open the oil cooler to help in cooling the entire system. I have observed this in my son's X3 3.5i, as well as my wife's, and my friend that has one and lives in Houston has observed the same thing. (See attached photo from the extreme heat wave in Southern California in September 2020). As such, I don't believe that you need to worry about the oil thinning out too much, unless you are seeing higher oil temps in actual operation.
Personally, I would lean towards the Mobil 1 0w-30 ESP with its BMW LL-04/MB 229.51/52 and Porsche C30/VW504.00/507.00 approvals. While I appreciate that BMW doesn't list LL-04 as approved, given the elimination of sulfur in the US fuel, this is not an issue. As others have pointed out, BMW is extremely slow to update their oil information. I recall it took BMW NA about 10 years to recognize that LL98 and then LL01 even existed.
Personally, given the weight and aerodynamics of the vehicle, I would be consider whether the 10,000 mile oil interval that BMW specs for the B58 should be shortened down to 7,500 miles or so to account for the additional fuel and stress the engine will see in ordinary use.
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