sythetic oils don't cause leaks, they just find them better than regular oils do. I used silicon (black) because I din't want to make another run to the parts store and it works fine. I would just suggest re-sealing it and letting the silicone set up for a good 20 min (or until it gets a slight skin) before bolting them together. Aslo maybe wait through the afternoon or untill the next day before you refill the case.
