Used auto parts can be a good choice when you need to make repairs to a vehicle, as they can save you quite a bit of money on those repairs. You might also find old, used parts that are no longer being newly manufactured. If you're not sure when to choose used parts from a wrecker versus new parts from a dealer or auto supply store, note a few considerations to keep in mind.
Some newer auto parts are made of plastic, or metal and plastic mixed together, to make them lighter and more affordable. While these parts can be very durable, metal is often preferred for pieces in the braking system, transmission, and the like. You might be able to find new parts made of solid metal, but they can be very expensive. Older parts are more likely to be made of solid metal without plastic mixed in, and will be more affordable, as said.
Rare or limited edition vehicles
Some auto parts can be cut and fabricated so that they fit other parts of the vehicle, and this can allow you to use them as necessary. However, if your vehicle is a limited edition, is very old, is a classic or is a rare model, you don't want to assume you can fabricate new parts to fit that vehicle. A vehicle may be a limited edition because several of its parts were designed and built in a unique way, and these parts may not easily fit something that you need to weld, trim, bolt or otherwise fabricate. Finding a used part that is meant for your vehicle in particular will mean less wear and tear on other parts under the hood, and better overall performance from your vehicle.
You don't know how to fabricate parts
As said, you may be able to trim or clamp a new part so that it fits onto your vehicle, but if you don't know how to do this properly, it's good to simply choose an older, used part that fits. You could cause damage to your vehicle by trying to fabricate parts improperly; for example, using a metal that is not heat-resistant can cause parts to become overly hot, and then wear down. Certain adhesives can also melt away, and then contaminate different fluid reservoirs. To avoid this potential risk of damage, only use older parts that are meant for your vehicle if you don't know how to fabricate new parts properly.