see also Conditioners

Note that in this article, the word oil is used to refer to both oil and oil-based grease products.

It is very important to remember that oil will interfere with polish to the extent that polish will not dry, will remain sticky, and will not take a shine if oil is applied to the leather. Oil should be used only on oil-tanned leather and boots that are being heavily conditioned, with the understanding that they will not shine following the use of the oil.

Oil should be applied generously to the leather via a cloth or by hand. After being allowed to penetrate and be absorbed by the leather, the excess oil is removed and the surface is gently buffed to even out the remaining oil on the surface of the leather.

Oils should be poured onto or (in the case of grease) scooped up with a cloth or bare hands and rubbed into the leather. All cloths used with oil should be very low lint, as lint will get trapped in the oil and detract from the appearance of the finished product.

Once the oil is applied completely to the leather, it should be allowed to penetrate the leather. Though the absorption begins immediately, allowing as much time as possible for the leather to completely absorb the oil is a good idea. Except for deep conditioning very dry or damaged leather, anything more than fifteen minutes will probably not be necessary and substantial absorption occurs in the first minute or two. Leather may completely absorb oil in some spots (generally the areas that flex the most: the ball of the foot, the ankle and the knee). In such a circumstance, oil can be reapplied to those areas.

Once the leather has been allowed to absorb the oil, use a clean cloth to absorb excess oil and to distribute the last remnants of the oil evenly over the surface. This will reduce the patchy appearance that is produced when the leather absorbs oil unevenly.