I agree to clean it and reseason it. Too much grease can make cast iron, 'tacky', or it can start to flake off. I know the OP knows the origin of this pan, but when I buy used-I reseason pans that have a big grease buid-up. Who knows the origin of that grease? If there is surface rust, I pour some Coke in a dishpan and soak it. Scrub it with a wire brush and reseason. It uses too much heat/energy for me to ever use a self-cleaning oven.