When should I use an alkaline, acidic or pH-neutral car shampoo?

Each type removes a different kind of dirt. pH-neutral shampoo is the everyday choice for regular maintenance washes: it cleans gently and is the safest for waxes, sealants and ceramic coatings. Alkaline shampoos and pre-wash foams break down oily and organic dirt such as traffic film, grease, bugs and road grime, so they suit very dirty cars and the first step of a decontamination wash. Acidic shampoos dissolve mineral deposits such as hard water spots and limescale, and are used occasionally rather than every wash. Use stronger products only when needed, follow the label dilution and never let them dry on the surface.