Ancient thread I can see, but just had this conversation over at M5 Board. Liqui-Moly 10W60 is good alternative to Castrol and MUCH cheaper.

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I LIKE OLDER BMWS, PLEASE HELP ME:
Fern Green 99 M3, Conforti Shark Software, Conforti CAI, Dinan Exhaust. Stamped LTWs, 235x40 square, OE Hella heads, ///M Pedal Kit, Clear Corners, OEM Rear Spoiler, CD43 stereo. MRegistry listing here.
Le Mans 2002 M5, Black/Titanium, Rogue SSK, Dinan exhaust, PSS9 coilovers, Euro rotors, iPod integration. MRegistry listing here.