Oiling is a process whereby leather is hand coated (usually by brush or tampon) with either a raw (un-emulsified) oil or a combination of raw oil, blended with emulsified oils and a penetrating aid.
Oiling provides the leather with lubrication to increase their softness[1] allowing it to flex repeatedly without cracking.
Leather fibres that are dry and un-lubricated break very easily.
Oiling does impart colour and an element of water resistance.
Oiling would normally be performed on full grain aniline leathers.