Just stick with the Shell or Chevron Delo 400 for 15W-40 oil. Or you could use Mobil Delvac 1300 15W-40. These come in 1 gallon jugs, which makes it easier (quicker) to do an oil change. Just dump in 2 jugs and your done.
The garage I bought my Porsche from said, 15W-40 is what they service all their customer's cars with, except for the Porsches, then they use Kendal 20W-50. This garage services all European makes. Rotella, Delo, and Delvac 1300 all can be bought at any Walmart or "McParts" auto parts store.

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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