If you're looking for something to do on the W123 and haven't done it already instead of changing the head gasket,...
Change ALL fluids,
Replace brake hoses,
Clean under the battery tray,
Vent the battery with an extended tube out and under the car,
Thoroughly clean all body drains especially those in the hood hinge pockets,
Replace exhaust hangers with MBZ genuine...

IMHO, the oil consumption is normal for a new car yet yours is a high miler. Just run yours hard once it's hot to keep the rings clean and prevent sticking.

Post some pics, I bet you're car is really nice.

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