What OEM Parts Are, and Why They're Important

Mia Bevacqua
February 6, 2019

When it comes to auto repair, your first instinct might be to save a few bucks wherever possible. One way to potentially do that is on parts. After all, how different can one alternator or wheel bearing be from another? The truth is, quite a bit.

There are hundreds — if not thousands — of parts retailers these days, each providing an array of product options. There’s original equipment manufacturer (or OEM), aftermarket and something called “OEM-approved.” 

We always recommend using OEM or OEM-approved parts. Let’s look at the differences, and talk about why this is the smart way to go.

What are OEM parts?

Anytime your car is serviced by the dealer, you’ll get OEM parts. As the name suggests, these components are identical — at least in theory — to what was on the vehicle when it was new.

OEM parts are made by the automaker, its supplier or its subsidiary. For example, Bosch (a supplier) makes fuel injectors for Volkswagen; ACDelco (a subsidiary) makes spark plugs for General Motors.

Choosing OEM parts has pros and cons:


  • Exact fit: An OEM part is a direct replacement for what originally came on your vehicle. As such, it should fit right. That makes the repair easier and guarantees the part will perform well.
  • Reliable quality: Although some beg to differ, most professionals agree OEM parts offer dependable quality. They can last longer and perform better than many aftermarket parts, potentially saving money in the long run.
  • Warranty: Typically, automakers back their parts with a one-year warranty. 


  • Costly: OEM parts usually cost more than aftermarket. That cost, however, is offset if the component lasts a long time. In other words: You get what you pay for.
  • Limited access: To get OEM parts, you typically have to either visit the dealer or order form a limited number of websites. Aftermarket parts, on the other hand, can be ordered from a variety of online sources, as well as local auto parts stores. 

» MORE: Get an estimate for your car repair

What are aftermarket parts?

Not all aftermarket parts are created equal. There are reliable brands (some of which are OEM suppliers) and then there are companies that crank out questionable products. Also, some aftermarket components are rebuilt, while others are brand-new.

Most independent repair shops use high-grade aftermarket parts — often referred to as OEM-approved — to avoid doing a job a second time without pay. 

Just like OEM, aftermarket components have pros and cons:


  • Less expensive: If you’re on a budget, some aftermarket parts will seem tempting, as they typically cost less than OEM.
  • Easy to get: You (or your mechanic) will find a wide array of aftermarket products available, either online or at the local auto parts store. 
  • Warranty: Aftermarket parts come with warranties, too, and sometimes the guarantee lasts longer than OEM. High-quality, aftermarket components sometimes come with two-year, three-year or even five-year warranties.


  • May not fit right: Nothing is more frustrating than a part that’s expected to fit but doesn’t. Even if you order a component that’s supposedly for your car, there’s still a chance it may not work. That means sending it back, delaying any repairs. 
  • Quality varies: One of the primary issues with aftermarket products is the quality variance. There are excellent parts (sometimes even better than OEM) and then there are those that are defunct straight out of the box. Independent repair shops will generally use high-quality components. But you can always ask what a shop will be using on your car. 

Verdict: Go with OEM or better

You can’t go wrong with OEM or OEM-approved parts. Avoid cut-rate aftermarket products — they’ll often cause more harm than good. If you have any questions about the components being used on your vehicle, talk with your mechanic.

Mia Bevacqua

About the Author

Mia Bevacqua is an automotive expert with ASE Master, L1, L2 and L3 Advanced Level Specialist certification. With 13-plus years of experience in the field, she applies her skills toward writing, consulting and automotive software engineering.

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