Car Shampoo. PROCHOICE® CAR SHAMPOO is pH neutral which makes it perfectly safe for all finishes while providing high lubricity and cleaning ability. It is suited to high-volume valet and production applications. PROChoice® Car Shampoo is also very versatile, well-matched to foam pre-soaking applications or two bucket wash methods. Dilution Guide: Bucket Wash â–º 25mL : 2.5L water Foam Wash Pressure Tank â–º 500mL: 50L Water