Are you serious? There is a huge performance drop between 91 and 87. Its very noticeable to me and certainly worth the extra $3 per tank. I don't treat my car any differently because I lease it.
I leased this last time because I found myself buying a new car every 2-3 years anyways. I don't feel there is any real difference between lease and own. The only minor difference I see is that I don't have the hassle of getting rid of the car when I'm ready for a new one.