The foam is better at maintaining its soapiness, and it is designed to retain its power and cleaning efficiency even when left for several minutes. ... So, make sure you use pre-wash foam and not shampoo during this important car cleaning process
Car Foam Wash is a concentrated pre-wash solution. It is formulated to loosen up surface dirt. When done right, foam wash will reduce the possibility of scratching and swirling the paint in your car.