I was reading James Martin's review of a 328i Modern (it was a shite review) and he loved it! On a long, multi-country mostly motorway tour, he achieved 55mpg with a car full of passengers and a boot full of luggage! It was the 8AT which will have helped but that is impressive! UK MPG obviously...
2006 BMW E60 520d SE 6MT
2009 BMW E90-LCI 330d SE 6MT
Current: 2012 F30 328i Luxury 8AT
2015 Audi A6 Avant Ultra, Black Edition (sorry!)