had a read

to summarize it seems the issue stems from very tight clearance between the bearing crank and conrods... in this case a thinner oil will help
also BMW NA have approved 5w30 5w40 and 0w40 oils for this engine
unless there there is bottom bearing shell wear on an S65 with thinner oil I see no reason not to run it on a street car and it will be better for the engine