Part of the issue is the bullsh!t CALIFORNIA oxygen rich gas. I have to suffer it too but when I leave the valley and get out east my gas milage will change in one tank of different gas. Proven 3 different times with 2 different vehicles.
2012 535i M-sport: Alpine White/AnthraciteTrim, Black Nappa Leather, Cold Weather, Luxury Seat, Premium Pkg, Premium Sound, Technology Pkg, ARS, 6 MT, HUD, Active Steering, 270 Cameras. 75% Llumar outside-100% Llumar inside.