I figured mine was from the Cam Sensor O-Ring, but the dealer did the tear-apart and found it was the valve cover seal. I don't know why it would start leaking after only 18k miles on it and never being touched, but what do I know? I had asked them to take pictures to show what the leak was but the tech that did the tear-down got in early and was done with that before anyone got in and asked him to document it.