Melmar, I have 2 minis also, Annie and Greta.
As for the mileage question, I'm not sure what you mean. I have not had an oil consumption issue at all, and I'm running Mobil for awhile now. Gas mileage is pretty normal for these vehicles from my experience.
Addendum: I only have 8000 miles. When we made the climb to the top of Grandfather Mountain in the Blue Ridge, the temp guage did climb, but the engine ran strong the whole way up. It was a very steep switchback type climb, and times we felt like we were looking down on the roofs of the vehicles behind us.