Many people are not quite clear about what OEM parts (genuine parts) and aftermarket parts actually are, and even seasoned mechanics can sometimes get confused by the details. This is perfectly understandable, as the automotive field is quite complex. Unless you are deeply involved in it—working for a car brand, dealer, or manufacturer—the finer points can be like a mystery. In this article, JAD will explain in detail the meanings of OEM parts and aftermarket parts, highlight the key differences between them, and help you, as a consumer, figure out which option may be more suitable for you.
| OEM/Genuine Parts | Aftermarket Parts | |
|---|---|---|
| Quality and Compatibility | Consistent quality and precise fit | Varying quality and uncertain fit |
| Price and Accessibility | High price and limited access channels | Wide price range and easy accessibility |
| Performance, Customization and Warranty | Standard performance with warranty coverage | Potential for upgraded performance, may affect warranty |
What Are OEM Parts?
Automakers Rarely Manufacture Their Own Parts
OEM parts, also known as genuine parts. Nowadays, most automakers rarely produce their own parts. Instead, they focus on design and assembly, entrusting the actual production of components to professional suppliers. For example, an automaker may not produce its own parts but purchase them from a company that excels in that field. In fact, some suppliers are so professional that almost every major car brand buys certain components from them.
Well-Known Cases in the Industry
Take brake systems, for instance. Many European brands rely on Brembo or AP Racing, while Japanese automakers often use Akebono. When it comes to transmissions, ZF and Aisin are the preferred brands. These companies that produce parts specifically for car brands are called OEMs (Original Equipment Manufacturers). The parts they produce and supply through official dealer channels are known as genuine parts or OEM parts.
Brand Logos Usually Not Visible
However, there is a situation: when these OEMs produce parts for car brands, their own brand logos are usually not visible. Moreover, whether automakers decide to produce parts in-house or outsource to OEMs depends on factors such as cost and technical expertise.
What Makes a Part “Genuine”?
So, OEM parts or genuine parts are essentially original components produced by the manufacturer responsible for that part—sometimes the automaker itself, but more often a professional supplier. When you drive a new car off the lot, every part on it is regarded as a genuine OEM part. It’s just that you can’t always tell whether these parts are produced by the automaker or its trusted partners.
Where Can You Buy Genuine OEM Parts?
For most people who are not professional car shop owners, there are mainly two ways to buy OEM parts.
- Go back to the dealer service center: Depending on the country or region you are in, you may not be able to buy parts directly. Some service centers may require their technicians to handle repairs and replacements.
- Buy online: With the development of the Internet, many brands’ OEM parts are now available for purchase online. It’s very simple—just enter the brand name plus “OEM parts” as keywords. Of course, it’s worth noting that not all automakers offer this purchasing method.
What Are Aftermarket Parts?
After understanding OEM parts, aftermarket parts are easy to comprehend. Any part that is not OEM is considered an aftermarket part. However, aftermarket parts can actually be divided into two main categories: OE-style aftermarket parts and performance/modified aftermarket parts. Let’s introduce these two types separately.
What Are OE-Style Aftermarket Parts?
- Purpose: OE-style aftermarket parts are components produced by third-party manufacturers that match or are very similar to OEM parts. Their size, specifications, and performance are usually very close to, and sometimes even exactly the same as, OEM parts. Whether they are similar or exactly the same depends on the manufacturer’s capabilities and strategies. The main purpose of OE-style aftermarket parts is to replace OEM parts, mainly because OEM parts are usually expensive.
- Price Range: Typically, the price of OE-style aftermarket parts is 50% – 70% of that of OEM parts. In some cases, you may even find that the price of aftermarket parts is only 10% – 20% of that of OEM parts. However, you need to be extra careful with these ultra-low-priced parts—they often come from factories in places like China, India, or Africa, where quality control may not be strict enough.
- Risks and Considerations: If these parts are things like seat covers or other decorations, the risk may not be too high. But when it comes to critical components such as engine or transmission parts, using low-quality OE-style aftermarket parts may cause serious safety problems.
OEM Companies Also Sell OE-Style Aftermarket Parts
As mentioned earlier, some OEM companies also sell OE-style aftermarket parts under their own brands. For example, shock absorber manufacturers like Bilstein and KYB are OEM suppliers for many car brands. In addition to supplying shock absorbers to automakers, these companies also provide the same or similar models to the public as aftermarket products.
The main difference is that when these OEM companies sell these shock absorbers directly, they do not carry the automaker’s logo. In other words, although these parts are produced by the same company and may be identical to genuine parts, they have not been certified by the car brand, so they are still regarded as OE-style aftermarket parts.
What Are Performance/Modified Aftermarket Parts?
This is a completely different field. Many people feel that their car is not perfect after buying it. Sometimes the power is insufficient, or the wheels, chassis, and brakes do not meet the owner’s expectations. As a result, car enthusiasts will try to modify their vehicles and upgrade to more powerful parts. These parts also belong to aftermarket parts.
Currently, the most common types of modified aftermarket parts include larger wheels, more powerful shock absorbers, larger turbochargers, and enhanced cooling components.
There are many brands offering these reinforced parts. Some factories independently develop products, and many performance parts actually come from OEM companies. For example, OEMs like KYB, Bilstein, and Akebono also provide reinforced parts specifically for modified cars.
However, it should be noted that in this field, price inflation is a serious problem, and there are too many brands for consumers and modification shops to choose from. If the technician handling the modification is not professional enough, the performance of your car may actually decline. The most obvious example is the large-size brake kit. Theoretically, a large-size brake kit does not necessarily shorten the braking distance, but we often see people claiming that their braking performance has improved after installation. Many technicians, car enthusiasts, and even some manufacturers of these reinforced aftermarket parts often do not fully understand vehicle engineering. Blindly installing larger or more powerful parts can easily disrupt the original balance of the car and end up wasting money.
3 Key Comparisons Between OEM Parts and Aftermarket Parts
Quality and Compatibility
- OEM Parts: Whether produced by the automaker or an external manufacturer, each OEM part is designed, produced, and quality-checked under the supervision of the automaker’s team, so it can usually guarantee a high quality standard. Moreover, OEM parts are specifically designed for your car model. As long as you confirm the OEM part number, you are unlikely to buy the wrong part, which saves time and reduces labor costs.
- Aftermarket Parts: The quality varies. Since there are many types of aftermarket parts, it is often difficult to know exactly which factory produced them. Sometimes even OEM companies may outsource production to other factories, so it is crucial to carefully choose well-known brands. In terms of compatibility, it is often unclear which genuine or OEM part the OE-style aftermarket parts produced by third-party manufacturers are based on. Depending on the type of part, the process of confirming compatibility can be quite complicated.
Price and Accessibility
- OEM Parts: The price is usually quite high. Generally speaking, the price of aftermarket parts is 50% to 70% of that of OEM parts. Moreover, their access channels are limited. For many car brands, you can’t simply walk into a dealer or service center to buy parts, and consumers often encounter obstacles. Although some brands now offer online purchasing services, not all automakers have this option. In addition, automakers will not supply OEM parts forever. Most brands stop providing OEM parts about 15 years after a model is discontinued, so you may encounter “out of stock” situations.
- Aftermarket Parts: The price range is large, with both low-priced and high-priced options. At the same time, aftermarket parts are very easy to obtain, with few restrictions on purchase. You just need to go to a dealer or search for your car model online. For older models, there is almost no need to worry about parts being discontinued, as there will always be factories producing aftermarket parts. Moreover, there are many brands of aftermarket parts, and you can choose the one that best suits your preferences.
Performance, Customization and Warranty
- OEM Parts: The performance is standard and can ensure that it matches the specifications of the car’s design, such as fuel efficiency, acceleration, air conditioning performance, etc. After replacing with OEM parts, the original performance of the car can be maintained. In terms of warranty, if your vehicle is still under warranty, using non-genuine (OEM) parts may be risky. Once a problem occurs, the automaker or dealer may refuse to provide warranty services because they cannot determine whether the problem is caused by the use of non-OEM parts. So OEM parts usually have warranty coverage.
- Aftermarket Parts: In terms of performance and customization, aftermarket parts can provide room for upgrading. Through appropriate modification, it may achieve performance beyond the original factory specifications, improving handling, power, braking, suspension, etc. But in terms of warranty, using aftermarket parts may invalidate the vehicle’s warranty. In addition, in some countries or regions, vehicle modification is illegal, and installing performance or modified aftermarket parts may violate local laws or emission standards, which may result in fines or failure to pass inspections. Moreover, in the used car market, buyers usually will not pay more for a car with expensive aftermarket parts. On the contrary, people may suspect that the car has been overused or abused, leading to a lower overall valuation.