Although water pressure can help clean, water alone cannot remove oil from dirty dishes. This is because water and oil do not bond. In order to resolve this chemical issue, the manufacturer of Dawn dish detergents adds chemical surfactants to many of their products. Chemical surfactants contain two sides: one side attracts naturally to water, while the other side attracts to the oil on dishes. The oil-loving side of the surfactant pulls the oil off of the dish, while the water-loving side attaches the molecule to the dish water. When you rinse the water away, it carries the oil away with it. The alkyl dimethyl amine oxide in Dawn Power Dissolver is an example of a chemical surfactant.
Since there is no oil to remove from the barrel when shooting BP, what is the dire need for surfactants in cleaning away BP residue?