I think it's 4250 rpm full load as per owner's manual, no load 4650 rpm for the W126 as per factory CD.

The way a 350 is set up from the factory, though. You don't get very good acceleration once you're past the 4K rpm hp peak. Power plummets very quickly.

I would go by the service CD.

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)