On the one hand, sunflower oil has high doses of E vitamin, which favor its longer preservation, as the mentioned vitamin has antioxidant properties. This fact prevents the sunflower oil from premature rancidity when used uncooked. When the oil is heated for cooking, it loses E vitamin and oxidation comes earlier.
On the other hand, as sunflower oil is a poli-unsaturated fat, it oxidizes easier than other oils with higher content in saturated fat acids. Due to this circumstance, it spoils before other olive oils