When you're faced with the prospect of repairing your used vehicle, you may be looking for any ways possible to cut costs. One such way is by avoiding the cost of a new part and instead performing your repair with a used or pre-owned part that can still provide years of reliable performance. However, not all auto parts are created equal -- and certain types of used parts may not be as durable as new parts. Read on to learn more about which auto parts you should purchase used, as well as the types of used parts you should always avoid.

Which used auto parts are a good investment? 

In general, any parts that are not "wear items" (such as brakes, tires, and belts) or that affix to the exterior of your car are a better investment when purchased used, rather than new.

• Body panels and interior parts

If your car is wrecked in an accident or sustains other damage (such as hail or a collision with a large animal) you may have been quoted what seems like an exorbitant amount to repair, replace, and repaint your vehicle's damaged exterior. However, in many cases you should be able to purchase pristine body panels or bumpers from a junkyard, and are then only responsible for the much lower cost of installation and paint. 

Interior body panels are also a good used option. If the hinge that allows your glove compartment to open and close breaks, or you lose your interior cigarette lighter, you may be able to find replacement parts at a very low cost if you investigate the used market. 

• Fuel tank

Unless you hit an enormous pothole, your fuel tank is fairly well-insulated from damage and has no moving parts that can cause problems. Purchasing a used fuel tank to install in your vehicle -- whether as a replacement or supplement to your original tank -- should provide the same value as a new fuel tank, at a fraction of the cost. 

• Exhaust pipes

Another great used item includes your exhaust system. This includes your muffler, as well as the exhaust pipes that carry soot and gas fumes away from your engine. These parts are fairly durable and don't endure much wear and tear. However, if your exhaust system begins to rust or develop small pinholes after years of use, it is often cheaper to replace the entire system rather than to make repairs. 

Before purchasing a used exhaust system, examine it carefully (both inside and out) for rust or tiny openings. Vehicles that are driven in climates that receive a fair amount of snow may rust more quickly due to the build-up of salt and other de-icing products on the undercarriage of your vehicle. Because rust spreads quickly and is not easily observed under a vehicle, you'll want to ensure that the used exhaust system you are purchasing is in pristine condition. 

Which used auto parts should be avoided?

In general, you'll want to stay away from the aforementioned "wear items," including windshield wipers, tires, and brakes, as well as any interior auto part that is primarily composed of rubber. Belts and hoses will become cracked and dry-rotted over time, so even if you are able to find a parts vehicle with very low mileage, you may find that these parts are not worth salvaging. And in some cases, used tires can even be unsafe. 

You'll also want to avoid purchasing used electronic components. These are much more difficult to check for damage than most other types of auto parts and, as technology increases, replacing electronic parts with newer and more improved parts becomes less and less expensive.

Keep these tips in mind, and you'll be able to save money and find the best used auto parts for your vehicle.