It's not oil. It's scratches and they all have them (I have enough of them to be quite sure, lol). I use perma blue paste to get them out, not 100 % but good enough. Amazon was the cheapest I could find. Only paste is good, not the liquid stuff.
Just widen the tabs on the upper hand guard, easy enough.
I think you misread. He said a coat of oil might take out the scratches.