Both are equally good. Amsoil uses Mobil 1 base stocks.

I use whatever I can get faster and cheaper, so far Mobil is winning their. All the local autoparts stores have the 0w40, so does your local MB dealer.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200