Though fish emulsion is not pure fish oil I used it several years ago to seal gaps and treat rust (make sure rust is bone dry) that is deep into a car body or totally inaccessible on two of my cars. It becomes tacky when dry, unlike mineral oil. Once the fish emulsion is dry the access can be cleaned off by oil removers and then the oil free metal bogged or puttied and painted over. Warning: Car stank of fish for some months,
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