Engine oil does more than lubricating the engine. It performs the function of protecting from wear, removes contaminants from the engine, acid build-up prevention, protecting the turbos, etc. For this, factors like the mixture and the thickness/thinness of the oil play an important role.
Usually, the engine oil needs replacement after every 5,000 - 15,000 kilometers. Or you can look for the following signs:
If the above signs are visible, it's time to replace the engine oil. But before choosing the oil, make sure that it is suitable for the engine of your vehicle.