Ideally, wash your car every few weeks. Hose off loose dirt first. Then use a sponge to wash the surface with a sudsy solution of water and a detergent made for car washing. (Don’t use household detergents; they may be too harsh and can streak a car’s finish.) Rinse the car, working from the roof down.
Remove bugs and road tar with a tar remover. Tree sap, bird droppings, and other stubborn stains may require a spot application of cleaner polish, a product sold for weathered car finishes. Rinse the car again after using any special cleaners, then wipe it dry with an old terry-cloth towel or similar soft, absorbent cloth. When to polish
Renew polish whenever water no longer forms into small, distinct beads on the flat surfaces of a car, usually every few months. Apply the polish according to the manufacturer’s instructions.
Spray-on, wipe-off products work well on new cars and those with finishes in good condition. If your car is more than 2 years old, chances are its finish has weathered.
In this case, use a cleaner-polish that contains a mild abrasive to remove the weathered top layer of paint. Wipe the polish off and buff the car’s surface by hand with a clean, soft cloth. (A power buffer may leave swirl marks.)