I'm getting 17-18 mpg at the moment which is incredible because 90% of my driving has been in heavy London traffic. My e60 managed only 12 mpg for the same drive. Got 349 miles out of my last tank - the e60 would never have come close.
Current Cars: M5 (F10) / Porsche 911 Turbo (997) / X5 40d Msport
Previous Cars: M5 (E60) / M3 (E46) / TVR Cerbera