Reconsider Synthetic, whatever your problem was had nothing to do with your oil being synthetic. Don't take my word for it, pose that question over on the oil site (bobistheoilguy) and I bet 100% of the oil guys tell you synthetic oil had nothing to do with your leak. Most group 3's like penzoil Platinum or Mobil One are made of the same exact things as your conventional oil, they just take out the impurities. Even better group 4 and 5 oils will have better film strength at operating temps and no impurities. You wouldn't purposely use a dirtier gas when a cleaner one is available, you wouldn't use dirty water in your cooling system when distilled is available, so why use the dirtiest oil?
I'd change it now, and use synthetic media filters.