The Barrel comes with a very strong oil or grease product, and you will need to use alcohol ( or Gasoline) to get it out. Acetone also works( Brake cleaner) but both the Acetone and gasoline should be used out of doors, with you staying UP Wind of the stuff. Don't breathe it in, and protect your hands and arms so that the acetone doesn't get on your skin, either. Most of us have suffered gasoline "burns", so I don't expect I need to warn you about that.
I recommend using a Vegetable Based oil in the bore for normal maintenance. If you are going to store the gun, then use something like Sheath to protect the bore during the long storage period. There are highly processed petroleum based oils, like Ballistoil( Mineral oil with additives) That work in BP gun barrels, but I still recommend that they be FLUSHED out of the barrel with alcohol, before the gun goes to the range.
There are also modern synthetic oils that will work in BP gun barrels.
The problem with using any petroleum based oil in a barrel that will shoot black powder is that the burning temperature and LENGTH OF BURN is seldom sufficient to Burn Petroleum oils or grease completely. That leaves a Tar-like mess that DOES require using an Alcohol solvent to remove. If you happen to use this in a Percussion gun, the "GUNK" may get back into the flash channel and nipple, and it WILL stop the gun from shooting. Then, you have the gunk, a loaded gun, and no way to fire the stuff out. Pulling a PRB or bullet from such a gun can be a dangerous process( have done it, but I first pulled the nipple, and ran alcohol, then water down to "KILL" the powder charge- and removed almost all of it----before I began pulling the ball.) Now, you can buy a CO2 device that will blow the PRB or bullet out the gun barrel, once you clear the gunk out to open up a path to the blockage.
Its much simpler to find a Non-petroleum based product to lube your bore, or protect it from rusting, and to flush all of these products out with alcohol before loading the gun. :thumbsup: