Avocado oil is what I use. It has the highest smoke point of the readily available cooking oils, is supposedly healthier than other oils, has a clean flavor and doesn’t peel once polymerized for me. Olive oil works, and so does various other fats; bacon, tallow, butter etc.

I use my cast iron more than any other pans because it is more versatile than my carbon steel or stainless steel pans. Each have their own place but cast iron works for more of what I do. The cast iron absorbs heat and works well for doing high heat cooking so having an oil that doesn’t burn until higher temps gives more temp ranges to operate in. When an oil/fat goes past it’s smoke point it becomes a carcinogen and is unhealthy to breath/eat. So avocado oil’s smoke point just over 500° is better than olive oil at around 300°-350°f.