I can tell you right now that Rotella T isn't a full synthetic. It shouldn't hurt your engine, but it's not a full synthetic, it's a group III synthetic which means that it's just conventional oil hydrocracked to imitate a synthetic.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.