For olive oil to be considered extra virgin, it must have a free acidity level of 0.8% or less. This acidity is expressed as a percentage of oleic acid, a type of fatty acid naturally present in olive oil. The lower the acidity, the higher the quality of the oil. Sitia PDO is more versatile and can be used for cooking, while Sitia PDO 0.3 is ideal for dressings and dips.