When you replace a part on your car or truck, you will usually have a choice between OEM and aftermarket. Here is what those terms mean and how to decide between them.
What are OEM parts?
OEM stands for Original Equipment Manufacturer. OEM parts are made by or for your vehicle’s manufacturer, to the same specifications as the parts your vehicle was built with.
You will also hear the word “genuine.” Usage varies, but genuine parts are usually sold in the vehicle manufacturer’s own packaging and under its brand. “OEM” is also used for parts made by the same original supplier but sold under that supplier’s own brand. When you buy, it is reasonable to ask exactly which kind of part you are getting.
What are aftermarket parts?
Aftermarket parts are made by companies other than the vehicle manufacturer. They are designed to fit and function like the original part. Quality and price vary widely by brand: some aftermarket parts are built to match or improve on the original design, while others are built to a lower price point.
Other terms you may see
- Remanufactured parts are used parts that have been rebuilt and tested. They are common for components like alternators, starters, and transmissions.
- Used or recycled parts come from another vehicle. They can be useful for body parts and older vehicles.
How OEM and aftermarket compare
| OEM | Aftermarket | |
|---|---|---|
| Design | Made to the vehicle maker’s original specifications | Designed by independent manufacturers to fit and function like the original |
| Cost | Often higher | Often lower; varies by brand |
| Choice | Usually one option per part number | Often several brands and quality levels |
| Availability | Can be limited for older or discontinued vehicles | Often available for popular older vehicles |
These are general tendencies, not rules. The right answer depends on the specific part.
Will aftermarket parts void my warranty?
According to the Federal Trade Commission, a manufacturer generally cannot void your vehicle warranty or deny coverage simply because you used aftermarket or recycled parts. It would need to show that the aftermarket part caused the problem you are claiming. Read your warranty terms for specifics.
When OEM may be the better choice
- Fit-critical parts such as body panels and trim, where exact factory fit matters
- Electronic modules and sensors that must match your vehicle’s configuration
- Newer vehicles where aftermarket options may not exist yet
- Personal preference for the same part the vehicle came with
When aftermarket may make sense
- Common wear items like brakes, filters, and suspension parts on older vehicles
- Budget-conscious repairs, especially if you are not keeping the vehicle long
- Discontinued OEM parts, where aftermarket may be the only option available
A note on emissions parts
Replacement catalytic converters and other emissions parts must be legal for your vehicle and your state. California and several other states have stricter rules than federal standards, so always tell your supplier where the vehicle is registered.
Questions to ask before you buy
- Is this OEM, genuine, or aftermarket?
- Is the part new, remanufactured, or used?
- What warranty applies, and for how long?
- What is the return policy?
Get help choosing
Not sure which way to go? Call Rock Sales Parts at +1 646 244-2586. Tell us your vehicle and what matters most to you — exact match, budget, or availability — and we will help you weigh the options available. You can also learn more on our OEM parts and aftermarket parts pages.
Need help finding this part?
Call with your vehicle details — we will help identify the right part and let you know what we can find.