Pinpointing one thing people can do to maintain their car's value over time is hard. Richard Griot of car-care and tool supplier Griot's Garage says your investment can be best-served by "keeping its surfaces — the glass, trim, paint and wheels — clean."

Your car has many enemies, some visible, some not so much. Emissions from industrial plants are released into the environment, where they are transformed into nitric or sulfuric acid. When deposited onto your car, in either a wet or a dry state, these contaminants can eat paint and, in extreme cases, metal.

Temperature accelerates the problem. Acid from bugs, bird droppings, tree sap and even leaves becomes more active when heated. Metal retains heat when sitting out in the sun, which in turn increases the chances that these irritants will cause permanent stains when left on your car.

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And even though water is the best way to remove these contaminants, it can also trap them on metal surfaces if not removed itself, allowing oxidation to occur, which ultimately causes rust and corrosion. Sea or road salt exacerbates the problem by causing a chemical reaction that can accelerate pitting and rusting.

But all of these issues pale in comparison to time. The longer an offensive substance is left on your vehicle, the greater the probability and extent of damage.

So what, you say? A few war wounds on the surface on your car are endearing, right? Wrong! What it means to potential buyers — either through the resale market or a trade — in with a dealer — is that you didn't maintain the vehicle properly. This neglect can bring resale or trade-in values crashing to the ground, all because you failed to wash your car regularly.

The reality is that people often value material things based on . According to the folks at Kelley Blue Book, aesthetics is one of the top considerations when a person buys a car. And since more people are testing the pre-owned or used market these days, it is important to keep your car looking its best so it's worth more when you are ready to upgrade to a new car. A vehicle that has a pitted or stained finish or splotches of rust is a turnoff, and thus is worth less than a car that looks pristine, regardless of how you maintained the vehicle mechanically — sad, but true.

If you currently don't clean your car regularly, it's not too late to change your ways. Of course, the quickest and easiest way to a sparkling clean car inside and out is to take it to a detail shop for a professional treatment. But at $75 to $300 or more per visit, there's plenty of incentive these days to learn what you can do on your own to make your car look like a million bucks.

Before You Start

Mike Pennington, director of training for Meguiar's, a leading producer of car-care products, says you should wash your car once a week. "Your car is constantly bombarded with contaminants such as tree sap mist and bird droppings," Pennington says. "If the contaminants are not removed quickly, they can bond to the paint and even etch the paint." However, there are certain things to consider before you break out the sponges.

If at all possible, park your vehicle in the shade. Washing your car in the sun can cause some surfaces to dry faster than you may want them to, leaving residue and unwanted streaks.