When you encounter a motor oil leak, it requires immediate attention, because, if left un-checked, engine damage can result. Some leaks can be corrected by regularly tightening bolts around gasketed surfaces, because a great number of leaks are caused by gaps between gasket surfaces. Moreover, gaskets will shrink, and/or harden with age. In this case, the gasket can no longer prevent oil from seeping past it. Use of an oil leak sealer can help with this problem. Other leaks are caused by failing bearing seals. For a permanent fix, the seal must be replaced. However, oil leak sealers can be used to stop and prevent leaks from seals.
For more info, see How to Stop an Oil Leak