What are preaseasoned cast iron pans preseasoned with? I'm shopping for new pans right now and keep seeing cast iron advertized as "preseasoned".  What does this mean?  What are they preseasoning it with?
They're pre-seasoning with some sort of fat. It varies by manufacturer, though soy is probably fairly common (its both cheap and has a high iodine value). For example, Lodge uses soy oil.