I'm using Mobil 1 5W30. It's advertised as a high mileage version. It seems to be working fine. I'm not losing any oil, but I had my valve stem seals and valve cover seals replaced a little over 1 year ago.

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Mike Heath
1988 560SL Black/Palomino
1988 300SEL Black Pearl/Burgandy
1984 500SEC Anthracite Grey/Palomino