This thread is old, but just throwing it out there...

You'd have to be out of your mind to run anything less than 91 in the MCS. Even with 91...I think is not enough for this car. 93 should be minimum...but us west coast folks don't get that option ugh. For what comes out to be about a $2 difference per tank...just use the good stuff!!

I cringe at the thought of running 87 in it...must run like complete crap...I'd hate to hear how badly it pings too. That motor will not be happy down the road. Oh and yes, schatzy, MINI has been known to deny warranty claims based on fuel used. It's been discussed many times on this forum. Just last week when I took my car in, my dealer asked multiple times what type of fuel I use...91 shell or chevron only.

And for those that say 100 octane is a waste and doesn't do anything, wrong. It does WONDERS on this car...try it.