Way back 150+ years ago when the Petroleum Industry was just starting up how do you suppose shooters and gun owners used this new fangled product? Was this "oil from the ground" pretty much accepted or looked at with suspicion?
I would tend too think people would have experimented with the “new” product, just as we do.... looking for a better mouse trap so too speak.
As stated above, if it works for you that’s all that really matters .
I was taught to use 3 & 1 oil on guns, is it the best oil out there... not likely but it worked.
That was in the 60’s -70’s,now I use Barricade and “I” have had great results with it... no rust.
I know a Gentleman who only uses motor oil.
He uses it in the bore, on the exterior of the metal and on the wood.
Right or wrong , it works for him.
He is in his mid 80’s, and I don’t think anyone can change his mind.
By the way he was a State Muzzleloading Champion when he was in his late teens,
So it’s not something he just started doing.