Only in specific cases. Full-strength car-wash soap is good for pretreating the bug deathscape on your grille or superdirt elsewhere on your rig, and more potent batches of car soap will make short work of deeply dirty areas of your car. In most cases, however, too much in the mix can leave a film on your vehicle – that stuff is thick and clingy, and wants to stick around. Use about an ounce of car wash per gallon of water and you’ll be fine. Fortunately, Mothers car-wash soaps – at any strength – will not harm your automobile’s paint.