2009 Xdrive 4.8i oil leak: oil cooler thermostat or timing cover gasket, pic included

[SeanC]

Long time lurker, I knew this day would come. Started developing a small oil leak about a year ago, dealer said lower oil pan gasket. Tightened the bolts a bit, and the leak slowed down significantly. Last week I finally changed the lower oil pan gasket when it was due for an oil change. A few days later, the leak is back about a few drops every night, and there is fresh oil on the e10 bolt that is visible above the side of the front diff.

After searching, I think it is either the timing cover gasket or the oil cooler thermostat gasket. Here's the view:



Any ideas? The car is a 11/08 built X5 with the N62 engine. 78k miles.