My opinion only but “returns 35+ mpg” to me does not mean on a 1 long run with optimum speed and conditions. I know it’s human to quote the best figure you have achieved but in the real world, it returns what the average mpg shows over a few thousand miles and that isn’t 35+mpg.
I had a 335D x drive that was supposed to average 51mpg, I really tried to get it close to that and the best I got was 44 mpg on 1 journey. Real time average over a few thousand miles was 38.