The brief
This 6 Series (the F13 coupe) came in with oil weeping from the top of the engine, spots on the driveway and the smell of oil cooking off under the bonnet. He brought it in to get it sealed. BMW engines run hot, around 110 to 120 degrees, hotter than a lot of other engines, and that heat is hard on rubber. The valve cover gasket seals the cover that sits on top of the cylinder head, keeping the oil in around the camshafts and the spark plug wells, and after years of that heat the gasket hardens, loses its squeeze, and lets oil seep out. The worst of it runs down the side of the engine, and some can pool in the plug wells. A hardened gasket doesn't reseal, so it gets replaced.
The diagnosis
We cleaned the engine down and ran it to confirm the source, the oil was coming from the valve cover gasket, hardened and weeping, running down the block from there, not from the oil filter housing or the crank seals which were dry. That's a valve cover gasket replacement with a fresh gasket and the area cleaned up, rather than chasing a weep that only spreads.
The work
The valve cover was unbolted, the old hardened gasket removed and the mating faces cleaned, and a new genuine BMW-spec gasket fitted, the cover torqued back down in sequence to the manual figures so it seals flat. The spark plug wells were checked clean, the area cleaned of old oil so any future weep shows up, and the level checked and topped. A road test and a check on the lift confirmed the engine dry, no drips, and the level holding.
The outcome
No oil leak, no drips, no oil burning off under the bonnet, the engine dry, and the level holding between checks. The 6 Series went home with the leak sealed. A hardened gasket only weeps more the longer it runs, so replacing it and cleaning up the area fixed the leak properly and made the next inspection straightforward.