When I bought the car the my dealer filled with 87 and told me it would be fine to continue doing so. On my first fill up I switched to 89 and didn't notice any difference in power. However for peace of mind I'll be sticking with 89.
Same here (except I do Shell 93)
No 91 here or I would get it, just 87/89/93.
That said I've been thinking of trying the half tank 89/half tank 93 that some have said they use, it just seems everytime I need gas I'm in a hurry so I just get a half tank of 93 and run.