2006 e90 318i Oil leak?

Hey guys, I had my oil changed last week in my 318i but the mechanic accidentally refilled with 6L Oil when the capacity is 4.25. I realised this straight away and had it drained and refilled the following day to the correct spec. Think I drove less than 40 miles with the 6L in.

The stupid oil checker failed to notice to overfill and still showed less that max on the display?!? but there was no symptoms i.e burning smell or smoke etc.

since having the oil drained and refilled what I've noticed on a few occasions is the smell of burning oil in the cabin, upon popping open the bonnet and nosing around I noticed this patch of oil.



I don't know if this was already there before the oil change or not but I will try cleaning it and seeing if it reappears. Can anyone shine any light on where this might be coming from and how much i'm looking at to get it fixed.

Also, my engine seems to sound like a diesel, Is this normal for a n46 engine??

Thanks in advance.