Removing Oil Stains From Leather
On finished (pigmented) leathers the oils should just wipe off unless it had time to soak in. On most leathers the oils will dissipate, over time. The amount of time depends on what type of leather you have and how much oil absorbed into it.
You can assist the leather in dissipating the oils by proper cleaning and using corn starch as follows.
Never scrub the leather as that will remove the finish in many cases. Some oils will soften the surface dyes making it easier to damage. Lightly clean the area but do not spot clean. If the stain is on a cushion clean the entire cushion, if it is on an arm clean the entire arm. The cleaning will remove the oil on the surface, the oils that have soaked in need to be pulled out and this can be a slow process.
To help remove the oils that has soaked into the leather, clean, rinse and condition the leather. The conditioner will help move the oils to the surface for the next cleaning. The oils will also slowly dissipate through the leather as well. Doing numerous light cleanings and conditionings over a few days to weeks will safely take out most oils. Use the right type of conditioner for your type of leather.
In between cleaning you can put a layer of dry corn starch over the oils stain. This will help pull some of the oils out. The best is to put on the area rub in and leave over night. Remove the next day and repeat as often as you like. On some stains you may find that you need to remove the corn starch with a damp cloth.
On some types of leather especially oil pull-ups you will notice that the leather is darker. The oil may have actually darkened the leather back to its original colour, especially if it has not been maintained and allowed to dry out. Check for fading by looking at any hidden areas of leather like the sides of a cushion. In this case repeated conditionings may bring back the colour to the entire piece.
Be patient as most oil stains will come out over time with little or no damage to the leather.