I've always oiled my grates, SS, CI, or PC.
And especially rusty grates.
I like to use a rag with oil on it, because sprays seem to make a mess.
If I oil, and things stick, at least I tried. ;)
Years ago I use to burn my grates off. I got told not to do that.
So I scrape and brush, and preheat, oil and go.
Probably doin it wrong. But nobody is layin in my yard dead.