I had this exact same conversation with my independent German-American mechanic
about one year ago, regarding my 1991 560SEC that had 118,000 miles on it and had been maintained with dyno oil, and the timing chain changed at about 100,000 miles..

His response was to stick with with the dino oil, on a car that had been using it that long, for the reason that the detergents in the synthetic oils were rather aggressive, and changing over to dyno oil would loosen things up to the point that new leaks would probably appear after such a change.

That logic convinced me to leave well enough alone and stick with dino oil..

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1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ...

1995 E 420, 170k "The Red Plum" (sold)

2015 BMW 535i xdrive awd Stage 1 DINAN, 6k, <----364 hp

1967 Mercury Cougar, 49k

2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive (sold)