The rule of thumb is any oil that is not natural to leather should be avoided. Synthetic oils, chemical oils, and petroleum based oils such as silicone, mineral oil, mink oil, and Neatsfoot oil can cause leather to dry out, crack, and become distressed. Back in the day, leather smiths swore by Cod Oil as the best preservative for leather.
When choosing the best leather care product, the first thing to remember is that leather is an animal skin. And the care and feeding of leather must be consistent with its natural state to prevent drying, cracking, distressed leather, and rotting stitching. That means, NO chemicals, NO mineral oil, NO neatsfoot oil, and NO paraffin. Only pure beeswax, tallow, cod oil, and pine resin, were the accepted ingredients for preserving and waterproofing leather. Trappers, loggers, hunters, and especially the military knew the importance of preserving leather and stitching. Ole Time Woodsman has recreated the exact formula that those who relied upon dry and long lasting footwear once used.