Obtain the proper detergent for the situation. Cleaning oily items, such as a car engine, require a detergent that includes a degreaser. Cleaning a painted surface, such as house siding, requires a more general-purpose detergent. Follow the manufacturer’s instructions for application rates and precautions.
Apply the detergent to the object to be cleaned using the lowest pressure setting possible. Set it to provide an adequate volume of water and detergent to create a full pattern of spray. The low pressure of the water allows the water and detergent mix to adhere to the object, rather than splashing off as it would if sprayed at a higher pressure.
Rinse off the detergent with the power washer set to the highest pressure and volume settings. Operators of a hot water power washer can also increase the temperature of the water for the rinse cycle.