A veteran leatherworker suggested Fiebing's Saddle OIl because unlike neatsfoot oil it is non-staining. Makes sense cause if you use it on your saddle you wouldn't want it all over your butt !
I believe he was meant it does not darken the leather.The Lexol Neatsfoot does not either.
Olive oil, canola oil pretty much any vegetable oil. Just put it on with a soft cloth and don't be stingy. Let set over night, and buff with another dry cloth the next day.
Vegetable oil will turn rancid over time