83k mi on my wife's 2001 X5 3.0,bought it at 78k mi in Nov 2010. I'll do some preventative maintainances like VCG, spark plugs, Vanos seals, clean ICV and throttle body, cooling system overhaul.
The car calls for 91 or higher, so that's what it get. I dont want to save a few bucks for any potential risk.