On the later W126's it doesn't work, but on the eary ones it might if you have the original metal cap. If I remember correctly I tried it on my 82 SD and it didn't fit, but I could be mistaken. I know for a fact that the new plastic oil cap that MB sells won't work.

However a rag in the valve train at 3k+ would probably destroy the engine.

Edit: just saw it was a W116, they might swap.

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