Here they are smoothing the underbody panels:
Mercedes E-Klasse: Sicher und getarnt - Bilder - Fahrerassistenzsysteme - FOCUS Online
Yeah, that's well-disguised. Good job!
In terms of the fuel economy keep in mind that, unlike the new EPA figures, the European "EPA" driving cycle is unrealistic because it's a synthetic, non-road-data-based test that in recent years has been delivering overly optimistic figures compared to the real world to the tune of about 1 L/100km, which means the Benz's 5.3 may be more like 6.3 L/100km (37 mpg) in the real world, but that's not too shabby, either.
The European "EPA" cycle has relatively few, low-speed simulated highway passages, which explains why the Europeans hadn't been doing as much as they could aerodynamically.
On a German page they mentioned some of the efficiency changes:
> Better engine
> For the sedan (Cd= 0.25): 4% better Cd compared to previous model = 0.25 L/100km less fuel consumption at 130 km/h
> "Venetian blind" controlled air vent behind the grill a la BMW
> 17% less rolling resistance tires
> Efficient controllers for accessories (alternator, fuel pump, A/C compressor, power steering)
> Stop/start function
(By the way here are some nice historic wind tunnel photos:
Die Geschichte der Aerodynamik - Vom Winde verweht - Klassik - autobild.de
)