More than one-third of car owners use damaging non-automotive products when washing their cars-products that could contain harmful detergents, abrasives and additives. And almost half of motorists don't ever wax their vehicles.

"Waxing at least twice a year is recommended for maximum protection, yet surveys show that 48 percent of motorists don't wax their vehicles at all," said Jeffrey Webb, director of retail marketing at Turtle Wax, Inc. "That's leaving money on the table at trade-in time, as a clean, well-maintained car can be worth up to 50 percent more than one in 'fair' condition, according to the Kelley Blue Book."

Motorists should avoid dish detergent, which contains harsh chemicals that, intended to cut through grease, will strip away the wax finish on your car. Some are hard to rinse off and leave streaks. For best results, a formulated automotive wash is recommended, one that gently lifts the dirt and grime while protecting the finish.

Washing an automobile on a regular basis protects it from the natural elements that harm the finish. The Car Care Council recommends the following dos and don'ts when it comes to a do-it-yourself car wash:

• Don't wash cars in direct sunlight. Do wash cars in shade or in cooler temperatures in the early morning or late afternoon.

• Don't use dish detergent. Do use a formulated car wash.

• Do fill your bucket with warm water.

• Do use a soft terrycloth towel or washing mitt.

• Do spray the car often with water.

• Don't scrub the car all at once. Do complete one section at a time, rinsing repeatedly to prevent the soap from drying on the paint.

• Do use soft terrycloth towels or scratch-free fabric to dry the vehicle.

• Don't neglect waxing the vehicle. Do prep the car for waxing using cleaner/polish to remove contaminants.

"The myth of not having to wax your car because you have a clear-coat finish is just that, a myth," Webb said. "Clear-coat finish is only as thick as a piece of paper and can become damaged from the effects of sunlight, UV radiation, acid rain, salt, dirt and air pollution."