I am talking about stubbornly oxidised (sticky, greasy, baked on) pans here. I've had a bit of success with vinegar and bicarb, but I was musing the other day about really strong detergents. Then it struck me: SWARFEGA!! I bought a tub, dipped my washing up brush in it and scrubbed out a griddle pan. Even the top edge that I'd virtually given up on came clean straight away! I was concerned about the smell of Swarfega remaining behind, but a good wash with Fairy and rinse worked.