some oils have petroleum distillates which depending on what type and how much can be aggressive to plating and blueing and scales,i guess that's why they recommend camelia oil which should'nt damage the plating or scales,the water where i live oxidizes certain carbon steels on contact so i get discolouring on some blades no matter what,if the oil used doesn't deactivate the oxidation it will eat into the blade just like rust does so i'd start using a different oil