If you notice milky oil inside your engine, it's crucial that you take action ASAP. This is what happens when oil and coolant mix with one another, which is quite bad for your engine should you ignore this issue and keep on driving. Milky oil won't lubricate or cool your engine as well as it did. Thus, potentially causing extensive damage if you don't fix it in time or keep the engine running afterward. To fix this, the entire engine needs to have all this milky oil flushed. But before you add some fresh, new oils in, you'll have to fix the underlying issue of how it appeared in the first place. Usually, milky oil is caused by a blown head gasket. So, replacing this head gasket is a key priority that you'll have to perform before adding some new motor oil.