Was the car serviced per FSS with dino for the first few years? If so there is the reason. 7k changes with Mobil 1 are certainly not causing this.

A quart every 2,500 isn't that much though, I'd just add and drive.

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2006 CL500
2009 C300 4matic
1969 280SE
2023 Ram 1500
2007 Tiara 3200