Quote:
Originally Posted by Radiation Joe
There are reasons and that is why some of us run different oils. The viscosity of the TWS is ridiculous. It's so thick that it shears down to 50 weight during normal use. Take it to track and it probably ends up even lower. I can run 40W Redline at the track for 40 hours and still have 40W when I'm done. On the street, I run what BMW originally designed these engines to run; 5W-30.
BMW builds tight tolerance engines. 30W oil is appropriate for engines built this way. The TWS is an insurance policy by BMW for people who take their cars to the track with 12k miles on an oil fill. When I built a hi-po M10 many years back, I built it with very loose (by BMW standards) clearances. I ran 50W oil in that one. The S65 is built for 30 or 40 weight oil.
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While you may find a reason not to run the oil specified, I really don't see the need to go out of the way to do so. You are pretty much talking from a track oriented use only. The average user doesn't need to use something different just for the sake of it. Redline isn't any easier to acquire than the Castrol so there is no benefit there from a strictly ease of purchase standpoint. Can you use another oil and not kill the car? Sure you can. Should you? I can't think of a reason why. Like I said, with the oil change intervals being so long, the costs of using something else just don't make much sense in my mind.