Your Avatar is hilarious. It looks a miniature battery operated version for kids.

In other news, the S5 is heavy because audi's are heavy. I remember reading somewhere that the revised version of the B8 Platform is going to be significantly lighter in 2010-11 cars. I think I read that on this site.

 

Sometimes its difficult to compare different specs, because there is much confusion over gross vehicle weight, curb weight and unladen weight.

Looking at car and driver web site the weights for the CLK 55 and the Auto S5 are slightly different from your numbers

Merc CLK 550 -3720 Lbs
Audi S5 Auto -3935 Lbs

Still, its 215 lbs more, but for its size its not that heavy compared with previous Audi's. For example my 2000 S4 V6 Biturbo was the same weight, but smaller!

I am keen to see how this car performs in official crash tests - I suspect it will perform very well, since parts of the body are using very strong hot-rolled steel.

 

Also consider that Audi has more 5 star crash rated vehicles with better safety than all other Luxury makers. Even Volvo doesn’t compare to Audi in terms of safety.

On Audiusa.com it says the A5 3.2 tip weighs 3913lbs and the S5 tip weighs 4067lbs. The difference of the two is only 154lbs.