There are several oils that can be used to season cast iron, but there are a few factors to consider when choosing the best one. The oil should have a high smoke point to withstand the temperatures needed for seasoning, which are between 400-500 degrees Fahrenheit. It should also have a high concentration of unsaturated fats, which are optimal for polymerization and creating an even patina. Here are some of the most commonly recommended oils for seasoning cast iron:

• Vegetable oil: This is a popular choice because it is affordable and has a high smoke point. It is also readily available in most kitchens.

• Canola oil: This is another affordable option with a high smoke point. It is often used interchangeably with vegetable oil.

• Grapeseed oil: This oil has a relatively high smoking point and an impressive amount of unsaturated fats, making it a good seasoning oil. However, it may not be readily available in most kitchens.

• Flaxseed oil: Due to a well-researched, scientifically based article on pan seasoning, many prefer to use flaxseed oil as it offers the hardest, slickest surface. However, it can be prone to chipping and flaking.

• Bacon fat/oil: Some people prefer to use bacon fat or oil to season their cast iron because it adds flavor to the pan. However, it may not be the best option for those who want a neutral flavor.

Ultimately, the choice of oil comes down to personal preference. Some people prefer to use the same oil they cook with, while others choose an oil specifically for seasoning. It is important to note that seasoning is based on the science of polymerization, and the goal is to create a hardened polymer that bonds with the iron to create a shiny black patina.