What's the best oil for seasoning cast iron? Cast iron can be seasoned, re-seasoned, and re-seasoned again Shep McAllister FacebookTwitterEmail There’s a lot to love about cast iron pans, but one of the material’s greatest virtues is that it can be seasoned, and re-seasoned almost indefinitely, potentially extending its life and restoring its non-stick qualities for decades, or even generations. We’ve discussed how you should go about seasoning your skillet, but one question always sparks vigorous debate in culinary circles: what oil should you use to do it? What is seasoning? Before you choose a seasoning oil, it can be useful to know what exactly seasoning is. Essentially, it’s a layer of baked-on oil or fat that hardens and adheres to your pan through a process called polymerization. This layer of seasoning protects the metal underneath from rust (the kryptonite of cast iron), and also imbues the pan with nonstick properties.