OIL LEAK

[WJNB]

Just noticed oil on wheel hub & coming through holes in brake disc. Engine oil level looks as if it 'might' be lower than usual.
Taking (2012 SLK 250 55k mile ) to local independent most excellent Mercedes specialist Monday.
Could I be in for a nasty expensive shock?

[rgv250ads]

Probably a failing cv joint boot or something in the hub, bearing grease from a failed seal or grease from the actual wheel bearing. On most mercs the wheel bearings are adjustable, this may seep some grease fling into the hub and then outward to the discs. Highly unlikely to be engine oil.
As you're getting substances on the discs best get sorted asap, for obvious reasons.