As this is a '3' Series Forum, I was looking at this Series and specifically the Saloon Version (and also for the '5' Series) as I am buying a Saloon.
All '3' Series Diesel Tourers have a Cd of 0.31.
The '3' Series Petrol Tourer (328i) has a Cd of 0.32.
Again Cd for Petrol Version higher than Cd for Diesel Version for the '3' Series.
Tourers are less aerodynamic than their Saloon equivalents and have a 10%+ higher Drag Coefficient.
Present: Superman 330d sDrive M Sport + Toys
Ordered: Red Tornado Golf 7R 5 Dr, DSG + Toys