I have beem reading different forums on oil to use in my 540i sport and M5. The 2001 M5 is not clear but I did use M1 15W50 had no issues, of course I do not race or hot rod it around and change my oil once a year since I do not put that many miles on it. I recently changes to LubriMoly 10w60 purchasing it from Bavian Auto. No perceptable performance difference. However on my 540i (1997,217,000 miles) I have used M1 HM 10w40 and 0w40 the later leaking out on my driveway. After reading my OM it recommends API SG rated oils multigrades. So I have to belive that even with the new GF5 API SN coventional oils they have to be significantly better than anything available in 1997. I plan to go a dino HM 10W40 on my next change (every 3000 miles).