The healthiest type of oil to cook with and the one that is the most versatile is olive oil. However, you will need to ensure that it is extra virgin olive oil, and not the standard type. This basically means that the oil is not refined or overly processed. Extra virgin olive oil means that the oil has not been refined, which means that it is of a higher quality.
Extra virgin olive oil also contains a large amount of monounsaturated fats and some polyunsaturated fatty acids, which many studies have linked to better heart health. Olive oil has quite a low smoking point compared to other oils, which means that it is best for low and medium heat cooking. It is also one of the healthiest oils that you can use for baking purposes.