I know I used to wipe my firearms down after cleaning them with a clean rag with Hoppes 9 on it. It would leave an oily-finish that was like a real thin oil, making the bluing look real dark. The gun metal could go a year or two and still have that thin oil coating on it.
Not any more.
With the Hoppes 9 I use today (I buy it by the quart, cheaper that way), when I wipe my guns down with it, they end up being covered with a sticky substance, almost as if I tried to shellac the parts wiped down with a thin shellac that never quite dries properly.
All my life I have wiped my guns down with Hoppes 9, in fact, I think it used to instruct one to do that on the bottle instructions if I am not mistaken!