Mix the olive oil, castile soap, essential oil and water in the gallon jug. Shake well so the ingredients are combined.
Pour a small amount of the mixture into a spray bottle. Keep the rest for future cleaning purposes.
Test a small part of the cleaner on an inconspicuous part of the jacket to see if it ruins the leather. Proceed if the mixture does not discolor or ruin the leather.
Spray a small amount of the mixture on the trench coat. Rub the spray into the coat with a clean cloth. Buff the coat after the mixture is rubbed in until the leather shines
Hang the coat on a hanger designed for leather clothes and allow it to rest overnight before you wear it again.