Don't give up, it's only money.
What can I tell you?
The car is 9 years old & things go wrong ( even if they are pricey ).
I believe any additive that would seal a substantial oil leak, may also have a tendency to possibly clog the pick-up screen on an oilpump.
There, not much help from me, but lots of sympathy.

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2007 C 230 Sport.