If it's worn it will need a repair, most smart repairers can do this . Are is it just dirty? I'd recommend using a swissvax leather brush and cleaner , not the cheapest but highly recommended! Any pics of the seats?
If your not losing water Im guessin you don't do alot of motorway miles? Go give her a good blast down the motorway. Might be condensation mixing with the oil. Won't do any harm, keep a eye on your temp gauge and do a oil change.