I think I will try a run of Delo 400 for my next oil change, right now I am running Mobil 1 0W-40 Euro Formula, but fear the lack of a large zinc additive could be causing extra wear on my M103.

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2006 BMW M5 "Heidi" @ 109,000 miles
2005 MBZ C55 AMG "Lorelai" @ 165,000 miles
1991 MBZ 300E "Benzachino II" @ 165,000 miles
1990 MBZ 500SL "Shoshanna" @ 118,000 miles

(On the hunt for a good used M103 engine as of 6/10/23, PM me if you have one to sell!)