About six months ago my S420 developed a very minor oil leak. It is coming from the rear of the engine on the driver's side. I tried looking down from the top of the engine but I couldn't see any oil. I checked around the entire valve cover gasket as well as the entire cylinder head and nothing is leaking from them. It is coming from lower down on the engine somewhere.

So I crawled underneath the car to try and get a view from the bottom. I can see the oil dripping off of the bottom of the engine and onto the lower control arm, but I can't see its source. It is dripping off of the lower control arm right where it bolts onto the car. Since I couldn't locate the source of the leak I took it to the dealer to see what they thought, but they said they couldn't locate the source of the leak either. They agreed with me that it's not the valve cover or head gasket that's leaking.

Is there anything on the rear driver's side of the engine that's prone to leaking? It's a very small drip. It doesn't even drip every time I park. I'll typically see 3 or 4 drops a week on my garage floor and the oil level on the dipstick hasn't moved at all. Any ideas about what could be causing this? Thanks!