Hi,
Dan - Well firstly, my formal testing was done in these# engine Brands:
#Diesels;
Kubota (3 & 4 cyl)
Yanmar
Isuzu (C201)
MB (various)
Petrol (AC = air cooled)
#Onan (AC)
Mitsubishi (6G72 mainly)
BMW (AC)
BMW (various)
VW 2ltr
#Nissan (3 litre)
No issues were ever experienced with this product in 15W-50 (full diester) SE or 10W-60 (ester/PAO) viscosity as it has progressed to today. In its 15W-50 form it was red and had the characteristic castor exhaust odour (great, just like the MC race days as a teenager)
Some hundreds of UOAs# and tear down inspections were involved and 2000hr OCIs were the common denominator
Secondly, if the oil is specifically recommended by BMW then IMO it should be used!
BWM in NA recommend either the TWS or Formula RS (LL-01) versions for all S54, S62, S65 and S85 engines. If unavailable then 10W-40, 5W-50 or 10W-50 synthetics (Sj/Cf or SL/CF) may be used
For the S62 engine:
Castrol Germany recommends:
1998-2000 - Formula RS 10W-60
2000-2003 - 0W-30, 5W-30,0W-40 or a semi synthetic 5W-30
Mobil Australia recommends M1 0W-40
To me this suggests that M1 0W-40 or Delvac 1 5W-40 are good alternatives for normal use beyond MY2000
I can recommend Castrol's 10W-60 products for racing - they are the common products amongst privateers in Germany for instance - almost regardless of engine brand!