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OEM vs NOS: A Guide to Different Kinds of Auto Parts

Author: Jaylin Khan
by Jaylin Khan
Posted: Jan 27, 2020
auto parts

Every car owner knows that when it comes to replacements or upgrades, it’s best to choose top-quality auto parts. They may be more expensive, but they’re certainly going to last longer and therefore give you more value for money.

That being said, not every car owner knows the difference between different types of auto parts. Sure, it’s easy to find a reliable auto-parts supplier for brands like Chrysler, Dodge, and Jeep. But do you have any idea what OEM or NOS means? Below, we list and define some common kinds of auto parts to help you differentiate and figure out which one you need.


This term is perhaps the most familiar to everyone, even beyond the automotive industry. OEM stands for original equipment manufacturer. This simply means that the parts are made by the car manufacturer itself. Therefore, the parts you get are guaranteed to fit your car’s particular make and model. Note that OEM parts tend to be a little more costly than other types of auto parts. Still, paying that extra cost could provide you with more peace of mind.


As opposed to OEM, aftermarket parts are those made by a third-party manufacturer. They are very similar to OEM parts but it’s possible that you might not get as good a fit with aftermarket parts. This is because most aftermarket car parts manufacturers work with different car brands and models. However, what’s great about aftermarket parts is that you get a lot of variety, especially when it comes to things like bumpers and grilles.


NOS stands for new old stock. Simply put, a NOS auto part is something that was produced a long time ago but has remained unsold. They can also be results of excess inventory, and are often meant to be used by a specific car manufacturer for a specific discontinued car model. This makes a NOS part the "holy grail" of replacement car parts—especially if you’re maintaining a vintage model. NOS parts that are still in their original packaging will even fetch the highest prices.


NORS, on the other hand, it stands for new old replacement stock. NORS car parts differ from NOS parts in that NORS parts were made after a certain car brand or model got phased out. Unlike NOS parts which were manufactured for original use, NORS parts are intended to be used as replacements. In the same vein, NORS parts are more affordable than NOS parts.

Tested Used Parts

As the name implies, tested used parts are used auto parts that have been tested for quality. These are usually OEM parts that, for one reason or another, have been removed from the original car. Tested used parts are relatively cheap and are great options if your car is an old model with hard-to-find parts.

Rebuilt Parts

Rebuilt car parts are old parts, usually OEM, with only the worn or damaged components replaced. For example, you can replace an engine’s piston rings if they are damaged instead of replacing the entire engine. Therefore, using rebuilt parts can save you a lot of money. The main concern about rebuilt parts is that the components may show different stages of wear, which means some components may need replacing sooner.

During the lifespan of your car, it’s inevitable that you’re going to need to repair or replace a few parts. With this handy guide, it’s now easier to choose what type of car parts you need.

About the Author

Jaylin is a Staff Writer for Bizmaa focusing on business analytics, business systems, gadgets and other small business news. She has a background in information and communications technology coordination.

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Author: Jaylin Khan
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Jaylin Khan

Member since: Jan 25, 2019
Published articles: 17

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