Redline in older BMW V8

[Ken E.]

I switched to Redline in my 1995 540i mostly because the mechanic who rebuilt the engine in the '58 Porsche swears by it. Redline recommends 10w40 for my car, and that's what is in there now. The recommendation seems a bit arbitrary since very similar engines built after 1997 get a recommendation of 5w30. Redline bases their recommendations on BMW's oil recommendations which evidently took a sharp turn to lighter oil in 1998. Judging from my reading, the HT/HS of 4.7 for the 10w40 is a bit of overkill for my engine. Might I not be better served with 5w30 instead? Or should I just put my OCD to rest and go with Redline's advice?

 

[dparm]

Something to bear in mind is that Redline is very shear-stable. That means it does not thin out over time nearly as much as other oils. So if BMW recommends 10w40, they know that most 10w40s will end up as 10w30s by the end. Since Redline 10w40 will still be 10w40 by the time you change it, I'd say you could probably just go for the 5w30/10w30.

 

[CATERHAM]

Right, RL 5W-30 with it's HTHS vis of 3.8cP would be as thick as you'd ever need to go.