Believe it or not, there are 2 5W-30 synthetic oils on the approved list. However, they are oils that are not sold here. I agree that European car companies are more interested in engine protection than fuel economy. You will be hard pressed to find a European engine that calls for anything less than XXW-40. My VW Passat calls for 5W-40, and only to use 5W-30 if 40 is not available. I use Valvoline Synpower 5W-40 (A3 rated) For a good conventional oil, I would go with Castrol 10W-40 every 3K, for your V-8.

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