Natural materials are porous by nature, with a tendency to absorb liquid stains quickly. When oily salad dressing comes in contact with leather, the grease soaks into the leather, leaving behind a dark, discolored area. Fast action to remove the grease stain makes the removal process quicker, but even a salad dressing stain that's soaked in can be removed. The key to getting salad dressing oil stains out of leather is to draw the oil out of the leather in addition to cleaning it off the surface.
Lay paper towels over the leather surface to soak up excess salad dressing. Allow the dressing to absorb into the towels without rubbing and scrubbing to avoid spreading the stain. Discard soiled paper towels and continue to soak up salad dressing until it's removed from the surface.
Cover the remaining salad dressing stain on the leather with baby powder. Apply enough baby powder to completely cover the stain. Leave the baby powder on overnight to absorb the oily salad dressing residue from within the leather surface.
Brush the baby powder off the leather with a clean, dry cloth.
Mix 1/2 tsp. dishwashing detergent with 2 cups of warm water to make a mild cleansing solution. Dampen a clean cloth in the detergent solution then wring it out to remove as much moisture as possible. Wipe off the leather surface to clean it. Rinse with a damp cloth then dry the leather with another cloth before allowing the surface to air dry.
Moisturize the leather with an appropriate leather moisturizer. Keeping leather moist helps to maintain the condition of the leather and prevent fast absorption of stain materials.