Check the owner's manual for the proper weight. I doubt it will recommend 5W-30. Generally speaking, European cars call for the thick stuff. My neighbor's '91 Audi 100 calls for 15W-40 or 15W-50. For both of my Benzes the owner's manual says a good year-round oil would be 10W-40.

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member