I've been looking for stainless steel food cups for a while to replace the plastic ones that came with Butter's cage. Petco had them on clearance for a dollar each so I decided to grab a couple of them. When I unscrewed the wingnut I noticed it was covered in oil. Like that black stuff people use to lubricate screws. I was kinda shocked that someone would actually put that on a product made for animals. And also I tried washing it off but it wouldn't come off and ended up irritating my skin. So the question is: are they unsafe?