I'm not an ///M owner but I'm sucking fuel like crazy with the 50i X6 with performance package. 100 miles after fill up, I'm at 1/2 tank.
My OBC is down to 14.3 from the 17.5 I averaged driving home from SC. I should reset the computer to see what I'm really getting, there's no way it's 14.3. I was getting high 13s with the 4.8i E70.