As it is, Mercedes has made some wicked strides in diesel technology.
It is in the following:
E - sedan
R, ML and GL - SUV's
I've driven an ML 320CDI for about 10-15 minutes and saw 30 mpg out of it
I've driven an R 320CDI for about 500 miles and saw anywhere from 30-34 mpg.
I've had co-workers drive the E 320 bluetec and get in the 40's mpg. I read somewhere that a magazine saw 50 mpg but that was done with drafting, raising tire psi etc.... but still, 50 mpg in a 4,400 - 4,500 lb car ain't half bad
Mercedes will be meeting the emission requirements for 50 state legal diesels shortly.
Germany has a 4 cyl blutec diesel engine for the c=class - hopefully that comes over here. That was rated at 47 mpg
Germany also has a v8 diesel which I hear has around 550 tq which is hot!
There are also rumors of AMG (the high perf division of Mercedes) to add to diesel's