I have an old friend, and when I first met her, she was using peanut oil to condition her bridle and saddle. I don't see where any vegetable oil would do any harm. I have heard that neatsfoot will rot cotton stitching. In my years, I have used peanut, neatsfoot and Lexol on my tack, plus glycerin soap, Murphy Oil Soap, Mink Oil (Pecard) and...shudder...Vaseline. My granddad told me to use it on the saddle he gave me. "Before you put it in the case, rub Vaseline into the leather and it will be good as new when you take it out." Well, that 1918 Pariani doesn't look new, but it is still pretty darn good for its age.
I just don't think mineral based oils are what leather is crying for, though. I usually use Murphy Oil Soap, now, for cleaning and moisturizing. For knife sheaths and boots and the like, I may use Montana Pitch Blend sealer or Sno-Seal. The Sno-Seal is great on boots and stays in there longer than the Pitch Blend. I like the way the Pitch Blend smells, though, especially on hunting stuff.
Killdeer