I agree with what Mysticblue said..
It is amazing how people think...
If people had the option to use gas octane rating from 91 to 99.. people will always choose higher thinking the higher the number the better the gas for your high performance engine
I've used 87 and 89 octane with no problems... for few weeks most people here in NJ / NY had no choice but to use regular unleaded due to Hurricane Sandy's aftermath..
My X5 is running pretty damn good...