I have a 2011 E90 N55 which seems to have a significant oil leak somewhere on the left side of the engine. A squeaking belt assembly lead me to pop the hood and find the belt covered in oil with spattering all over the left side (see photos). I have heard that the oil filter housing gasket and valve cover gasket are common culprits. Does anyone have any suggestions on how to proceed? Are there any other possible leaks to look for? I'd like to take it in to my local indy shop (Strictly BMW, Bellevue) or the dealership, but don't necessarily want to just ask for a general investigation and end up with other needless/extra work and expenses.
