I always put Shell V-Power (91). I notice the fuel door actually says minimum 89. My previous X5 said minimum 91 on the fuel door.
I used to put Sunoco 93 (now Petro Canada) in my X5, but turns out that the extra octane rating is derived from adding ethanol. Shell V-Power has zero ethanol. I find that the BMW engines run better with fuels that have no ethanol.
2012 535 ix - Imperial Blue, Black Leather, Anthracite Wood