Because cars are built to spec for a reason, modifications can significantly alter resale value depending on the car.
The original parts fit perfectly because they were designed to do so. Engines, brakes, suspension, frame, and tires are all selected, manufactured, and tuned for specific characteristics that the manufacturer determined years in advance. Modifying a car destroys the design integrity of the vehicle and, if not done correctly, can cause much more damage. For example, you may want to make your car faster by modifying the engine. Engine modifications that alter the air/fuel ratios may cause the engine to run lean or rich, both of which cause long-term damage.
Are Modifications Negative?
Not always, there are some rare and circumstantial exceptions to this rule. Assume you own a car that has been modified to be a race car. Because of the modifications, your car is worthless to someone looking for a good commuting normal car. On the other hand, someone looking for a race car will be overjoyed with your vehicle.
By modifying the car, you are limiting the potential market, and this is true for style, performance, and any other type of modification. The next owner may not want a large stereo system, especially if it complicates the car’s electrical system, and aftermarket alarms are the same. This may appear to make the car safer, but if the car was not built with an alarm system in mind, installing an aftermarket one may cause catastrophic electrical problems.
Modifications of Various Kinds
Aside from racing, there are modifications that appear to be more stylish and enjoyable. For example, you can put small TVs in the headrests and increase the value, but only to the right buyer. A different buyer might see this modification as someone who wants to avoid any additional potential electrical problems. The same is true for aftermarket alarms. Someone may decline to purchase a specific car with an aftermarket alarm because they do not want to deal with any problems that may arise as a result of the car not being built with an alarm.
Modifications that improve on existing parts could be considered worthwhile investments. For example, the thermostat housing is made of plastic. These vehicles are notorious for failing cooling systems, so depending on who you ask, replacing that plastic thermostat housing with one made of metal could be considered a good modification that you can do to improve the vehicle. The impeller on the water pump, which is also made of plastic from the factory, is a part of that car that is generally not debatable. A water pump with a metal impeller could also be a good addition.
If you really want to modify your car, don’t throw out the old parts; in fact, if you plan to heavily modify your car, it might be a good idea to keep the car around for a long time. Examine your vehicle’s history, such as recalls and parts that frequently fail, and try to obtain better replacement parts.
A better braking system is a good general modification for any type of car. Simply switching to better pads, such as ceramic or metallic, will improve stopping power, and switching to cross-drilled and slotted rotors is also a good idea. Make sure to have your brakes serviced by a professional, as this is one of the most important parts of your vehicle that you don’t want to get wrong. Check that the parts fit and are designed for your specific vehicle.
Make Modifications Wisely
Make sure to do your research before you modify, and make sure the parts you’re replacing are a genuine fit. If your car manufacturer later made better parts that didn’t make it into your vehicle, use those instead. OEM parts are always the best fit because they were designed specifically for your vehicle. If you decide to make these modifications to your car in your own driveway, have a mechanic double-check your work.
Classic Cars for Sale can provide great resources for comparison.