Coupe bodied variants, more fuel efficient?

[ILoveMondeo]

Just idle pondering while trundling down the M6...

Are the coupe bodied variants of modern cars any more efficient due to improved aerodynamics? for example the Passat CC, 6 Series, 3 series, and all the rest, which are essentially a different body on identical engines, running gear, transmissions etc. as their saloon counterparts...

I'd have thought they weigh pretty much the same, they just seem to have a more slippery shape, if that makes sense..

Cheers