The subject ENGINE OIL is likely to result in a few objections from people that are against talk on this board.
I suggest you use the search button, enter "Synthetic" and see what you find. There is lots of info and talk on the subject (including things like Oh No! Not another Oil Thread...." )

That said, I use synthetic in my engines with tight rings, especially my '87 300D turbo (OM603 engine) which has hydraulic lifters that tend to plug if Dino oil is used, and in my '85 300TD which has a newly rebuilt engine. I use Amsoil exclusively now that they sell it in 2.5 gallon jugs.
I did not see what vehicle(s) you drive so can't comment directly on your cars.
If you have lots of blow by or are losing oil in a car then using synthetic is probably a waste, unless its cold weather then synthetic is what you need for those deep winter starts.
Dieseldiehard

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!