Olive oil does not go rancid as quickly as "cooking oil" or most seed oils, in fact, most seed based cooking oils (especially those used in restaurants) are already rancid.
I mix with beeswax, sometimes I add a little Murphy's Oil Soap, I shoot for a consistency of jello pudding while it is still warm. This results in a final product that is soft enough to be spread or smeared on metal or cloth, but does not pour or slop. I alter the amount of beeswax to change the consistency based on intended use, metal protectant I like a little stiffer, patch or wad lube a little softer and with some M.O.S. added.
I actually use it for other things as well. Without the M.O.S. I use it as a nontoxic protectant on my small daily carry sheath knife's carbon steel blade. If I know I'll be playing in or around water I add a little extra. When it is time to slice up something for lunch I don't have to worry about toxic oils and such. It is good on skin. Good for sealing and living things. I apply it to powder horn plugs when I know I'll be hunting in the rain, as well as sealing my flintlock's pan with it under the same conditions. I finish knife scales, wood pipe tampers, bamboo/cane powder measures, and wood container plugs with it.
I suppose one could use straight olive oil for patch lube when shooting at the range and not waiting to fire the shot once loaded. But, I think that would get messy as the wax keeps the oil in place.
Oh, you mentioned vaseline. I believe this is a petroleum product, I understand some use petroleum based products like petrol jelly and vaseline to seal the front of b.p. revolver cylinders. I would avoid it within the barrel of your muzzleloader.