Just a quick note here. In my experience, the most common cause of oil leaks is lack of maintenance, in particular, extended time between oil changes. As oil lives in your engine, it becomes acidic. When this happens, it breaks down the materials that gaskets and seals are made of. These gaskets and seals then become hard and brittle. They reach a point where they are no longer pliable, and as a result, they start to leak. The takeaway here is to keep your oil changed at the correct interval. You can extend the interval a great deal by using synthetic oil.
A word of caution: I recommend you start using synthetic oil when your engine is NOT leaking. If your engine has already started to leak, you might not want to use synthetic oil. In some cases, the use of synthetic oil can actually aggravate a leaking engine. The reason for this lies in one of synthetic oil’s strengths: its ability to flow under a variety of conditions. Synthetic oil, even of the same viscosity, flows better than conventional oil. What this means when you have a leaking engine is that you might find that your oil leaks get much worse if you switch to synthetic oil.
Please understand that I’m not saying that synthetic oil causes oil leaks. In fact, just the opposite. Synthetic oil has special conditioners to help extend the life of the seals and gaskets in your engine and help prevent them from leaking in the first place. This doesn’t always work, though. With some leaking engines, installing synthetic oil makes things much worse. So, to prevent leaks, change your oil regularly. If you have a leaking engine, installing synthetic oil MIGHT make things worse. Personally, if I have oil leaks on an engine, I stick with conventional oil and repair what leaks I find.
Here are a couple videos that talk about regular oil versus synthetic oil.