[aerohead]

1) The 2008 M-B Bionic Boxfish is the most efficient shape Daimler has produced.
2) The 2018 M-B A-Class is the second-best design.
3) The 2013 M-B CLA 180 Euro Blue is in third place.
4) There's nothing to prevent a CLS from being streamlined to a drag lower than a CLA 180 Euro Blue, but that would be on the owner of the car.
5) According to Dr. Teddy Woll of Daimler, the tail by itself could take the CLS down to Cd 0.221, with no other modifications.
A set of 4- wheel covers, like on the rear of the Koenigsegg Jesko Absolut would take the boat-tailed CLS below Cd 0.20.