Other petroleum by-products find their way into leather care products. That's not so good. Leather needs periodic conditioning with an oil-based product to lubricate it and keep it supple. But all oils are not created equal when it comes to leather care. The ideal leather conditioner contains a blend of oils similar to those in the fat liquors used by leather tanners.
Leather comes out of tanning solutions literally stiff as a board.
This emulsion of oil and water can penetrate deeply between the fibers of the boardy hide to make the leather pliable. While different tanners use different fat liquors, top quality leather makers use blends of animal-based oils to create the strong, durable leathers prized by horsemen who pass their tack from generation to generation. Over time, the oils originally tumbled into the leather fibers dry out, oxidize, or get flushed out by sweat, water, and repeated cleanings. The leather begins to get stiff again. So the oils must be periodically replenished to keep the leather strong and supple.