20w/50 because that's what BMW specifies -
use BMW # 059 oil filter, or MANN brand
'other' brand filters blow apart due to low burst pressure
cannisters. Your car developes up to 125+ psi during cold start/warm-up
lubricate your throttle piviots at every oil & filter change

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1976 BMW 2002 #2743711(sorry I sold it 12/25/06)
1986 BMW R65 650cc twin 19k miles
1964 BMW R27 250cc single 15K miles
2002 BMW 325xiTouring 29k miles
1984 MERCEDES-BENZ W123 300D Turbodiesel-188k miles fein-DIESEL