I have tried several pre-soaks during my short time in the car wash business, about 10. My favorite so far is Extreme by Scotch Plaid.This also can be used as a high pressure detergent which I like and have used it for that. Some are not dual purpose. Does anyone else use this product that has a comment about it? I'd be interested in your top pick of tried and tested pre-soaks. My wash is self-serve.