The terms
| Term | What it usually means |
|---|---|
| OEM (original equipment manufacturer) | A part made by or for the vehicle maker and sold under the vehicle maker's name, usually through dealer parts departments. |
| OE or OES (original equipment supplier) | A part from a company that supplies the vehicle maker, sold under that supplier's own name. It may be the same as, or close to, the part fitted at the factory. |
| Aftermarket | A part made by another company to fit the vehicle. Quality ranges from basic replacements to parts built to exceed the original specification. |
| Remanufactured | A used part rebuilt to a set standard, with worn components replaced. Common for alternators, starters and some brake calipers. |
| Used or salvage | A part removed from another vehicle, sold as-is or with a short guarantee. |
Sellers don't always use these words the same way, so ask what a label means for the part in front of you.
Trade-offs in general terms
OEM parts
OEM parts are designed for your specific vehicle, so fit is rarely in doubt, and the dealer can look them up by your VIN. They are usually sold through fewer outlets, and the choice is limited to the vehicle maker's own version.
Aftermarket parts
Aftermarket parts are widely available and come in many versions, sometimes with features the original did not have. Quality and fit vary between manufacturers. Some product lines are certified by independent bodies, and many carry a written warranty. Read the details of what is covered.
Used and remanufactured parts
Used parts can make sense for trim pieces, mirrors or body panels in the right color. Remanufactured parts are common for heavy electrical and mechanical units. For wear items and safety-critical parts such as brake pads, a used part is rarely a good idea.
Parts where the choice matters most
For brakes, steering, suspension, tires, airbags and seat belts, the quality of the part directly affects safety. Many mechanics prefer OEM or well-documented replacement parts for these systems, and some shops will only fit parts they supply themselves so they can stand behind the work. Airbags and seat belt components should only ever come from proper sources and be fitted by trained technicians.
Warranties and the law
In the United States, the Magnuson-Moss Warranty Act generally means a manufacturer can't void your vehicle warranty simply because you used aftermarket parts or had service done somewhere other than the dealer. The manufacturer can still deny a claim if it shows that a part or a repair caused the damage. The Federal Trade Commission publishes consumer guidance on this. Keep receipts and records of all maintenance.
Leased cars, extended service contracts and insurance repairs can have their own rules about parts. Read the contract or ask the provider.
Questions to ask before you buy
- Is this part confirmed to fit my exact vehicle, including engine and trim?
- Is it new, remanufactured or used?
- Who made it, and what does the warranty cover?
- Does the part need anything else, such as new bolts, gaskets, fluid or programming?
- Can I return it if it doesn't fit, and is the box needed for a return?
- If a shop is fitting it, will they fit a part I supply, and will they warranty the labor?
Our guide to finding the right part covers the vehicle details you need to answer the first question.