Some info about the fuel mileage between manual and automatics.
I am contemplating a SLK 230 Compressor next March and requested some literature from MBUSA.
For that model, the EPA ratings are:
Manual: 20 mpg (city) and 29 mpg (HWY). 0 - 60 in 6.9 s.
Automatic: 23 mpg (city) and 30 mpg (HWY). 0 - 60 in 7.0 s.
With the 320 engine (SLK32):
Manual: 18 mpg (city) and 27 mpg (HWY). 0 - 60 in 6.6 s.
Automatic: 21 mpg (city) and 27 mpg (HWY). 0 - 60 in 6.6 s.
So in this car, the automatic gets better fuel mileage. I have seen similar numbers from other makers as well.
Now for the C230 Compressor, the numbers are closer.
I remember reading from Car and Driver (?) that they cannot out-shift the automatic with the 6 spd manual, proving the point MB told them. I believe the tests were done on the C230 Compressor.