I found the perfect lube many years ago. Maybe 20 or so.... My wife bought it as an oil to treat her saddles. The info on the tub says "Harness Honey Leather Conditioner"....It is manufactured by Carousel Farm, Kearneysville, WV 25430 ....phone # 304-725-3909.
I have no idea if they still exist, or what it's composition is but I will say that I have never considered any lube since using it. I can literally reuse patches that have been shot....Hope this helps...Bill