Porsche is making use of aluminum fasteners for important engine components. These fasteners are substandard for the service. At 100,000 miles, two of the bolts for the timing chain cover simply broke in half during normal service, resulting in a substantial oil leak and an expensive repair (about $3000). At 120,000 miles, one of the bolts for the valve cover also simply broke in half, resulting in another oil leak and a repair bill of about $1000.