I would use original Mercedes-fluids..
In PS there's only so little oil anyway.. So 1liter of oil is cheap.. Also it's better regarding seals and so ..
In the transmission I would prefer original MB-oil.. But some say Dex III also is good.. ??
I will agree with you on the power steering fluid on the newer cars, but most independent shops that work on this era of cars use ATF in the PS system with no ill effects at all, and have done so for a couple of decades, or more...
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