Whether you have a car with a clear-coat finish or conventional car paint, your car can become dull through a chemical reaction between pigments in the paint and radiation in the atmosphere, called oxidation. Oxidation leaves a chalky residue on the car that can't be removed with washing and waxing. But there are many other ways to remove oxidation from a car.
Things You'll Need
Move your car to a shaded area or in a garage where the temperature is between 65 and 70 degrees. Do all your cleaning and detailing in this area.
Choose a fine-grit polish -- the higher the grit number the better -- or a product that combines a polish with sealant. You can find these at most auto parts stores. Make sure you buy the kind of polish that is applied by hand. If you have a clear-coat finish, there are polishes available especially for your paint. Apply the polish in a 1-foot area with a damp rag and rub it until the oxidation is gone. Use a clean, soft cloth to wipe the polish off. Finish each area before you begin a new one. This process takes time, but it's worth it.
Use a polishing compound on heavily oxidized car finishes. Use a clay bar to remove paint contaminants. Carefully apply a very small amount of a "fine cut" or "premium" polishing compound designed to put a final shine on paint in good condition. Both are available in auto parts stores. Rub very gently in a small area with a soft rag. Remove the compound with a soft terrycloth towel.
Try rubbing compound only if nothing else works. These are medium-grade polishes that are a bit more aggressive than the "fine finish" polishes you'd use on good paint. Carefully apply the rubbing compound with a damp rag, gently rubbing one square foot at a time. If you rub too hard, you'll remove the paint.
Use one of the restorative systems that offer step-by-step instructions and includes all the products you need. It's cheaper and you don't have to guess what products you should buy. Once you have the restoration system -- which will typically include a clay bar and the various grades of sandpaper and polish you'll need -- follow the directions given.
Shine your cleaned car with a transparent finish glaze. Apply the glaze with a clean, soft cotton cloth and let it sit. When it's dry, it should look hazy. Buff the glaze by hand or with a machine buffer. Follow immediately with a coat of wax to protect the shine and weatherproof the car's finish. Carnauba wax gives your car a wet-looking shine. Synthetic wax gives a glossy shine to your car. Both protect your car's paint from contamination.
If none of this works, the damage may be too deep for the usual commercial products.There's still a chance of salvaging the paint, but the damage may be past the clearcoat. The only way to know is to use a very aggressive bodywork polish, about 5,000 to 6,000 grit. These are meant to remove scratches from 1,000 to 2,000-grit sandpaper. These polishes can quickly eat through your clearcoat, though, so this is a last-ditch effort. Polish as you did with the milder abrasive, checking your work often. If you start seeing paint color on your polishing rag, you've eaten through the clearcoat; at this point, you'll know the oxidation has gone too deep, and a full re-spray is in order.
Note that a good number of vehicles use "single-stage" paints that don't have a clearcoat. With these, you'll see color on the polishing pad no matter what compound you use. Don't use heavy abrasive polishes on these; single-stage paints are thin and you'll go straight through to the primer with little to no warning. If these steps don't take the oxidation out of a single-stage paint, you're in for a trip to the paint shop.