Boy it seems a lot of you guys have crummy MB dealers in your area!!!
Both in the Dallas Texas and Columbus Ohio areas I have had great experiences. If for some reason I didn't, I got the service manager at the dealer involved and all was corrected quickly
As my car is a diesel they only fill it halfway between the two marks on the dipstick.
It seems to me that before I would allow a dealer to do something that would harm my car, I would at a minimum question the practice. If they continued I would involve the regional MB rep. If he doesn't correct it ,then at least all parties have been duly informed before you take legal action..... :-)

Warren
1992 300SD 118K
Columbus Ohio