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Many people aren’t quite sure what OEM parts/genuine and aftermarket parts actually are—even seasoned mechanics sometimes get tripped up by the details. And honestly, that’s perfectly understandable. The automotive world is complex, and unless you’re deep in the trenches—working for a brand, a distributor, or a manufacturer—the finer points can be a bit of a mystery. In this article, T.G.Q will break down exactly what OEM and aftermarket parts mean, highlight the key differences between them, and help you figure out which option might make the most sense for you as a consumer.
| OEM/Genuine Parts | Aftermarket Parts | |
| Price | High | Low to High |
| Quality | Consistent | Varies |
| Availability | Limited | Easy |
| Brand Recognition | Strong | Varies |
| Performance/Customization | Standard | Can offer upgrades |
| Warranty | Covered | May void warranty |
What Are OEM Parts?
Automakers Rarely Make Their Own Parts
OEM parts, also known as genuine parts. These days, most automakers rarely manufacture their own parts. Instead, they focus on design and assembly, leaving the actual production of components to specialized suppliers. For example, an automaker might not make its own parts—instead, they’ll source them from a company that excels in that field. In fact, some suppliers are so specialized that nearly every major brand turns to them for certain components.
Famous Examples 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 go-to names. These companies, which manufacture parts specifically for car brands, are known as OEMs (Original Equipment Manufacturers). The parts they produce and supply through official dealership channels are called genuine parts or OEM parts.
Branding Stays Behind the Scenes
There’s a catch, though: when these OEMs produce components for a car brand, their own branding typically stays behind the scenes. Moreover, the decision of whether to make a part in-house or outsource it to an OEM comes down to factors like cost and technical expertise.
What Makes a Part “Genuine”?
So, OEM or genuine parts are essentially the original components made by the manufacturer responsible for that part—sometimes the automaker itself, but often a specialized supplier. When you drive a new car off the lot, every part on it is considered a genuine OEM part. The only thing you can’t always tell is whether those parts were made by the automaker or by one of their trusted partners.
Where Can I Get Genuine OEM Parts?
For most people who aren’t professional car shop owners, there are mainly two ways to buy OEM parts.
1. Return to the Dealer Service Center
Depending on your country or region, you might not be able to purchase parts directly. Some service centers may require you to have their technicians handle the repair and replacement.
2. Buy Online
With the growth of the internet, many brands’ OEM parts are now available for purchase online. It’s simple—just enter the brand name plus “OEM parts” as your keyword. Of course, it’s worth noting that not all automakers offer this option.
Advantages of OEM Parts
1. Quality Assurance
Whether the part is made by the automaker or an outside manufacturer, every OEM part is designed, produced, and quality-checked under the supervision of the automaker’s team. This means you can generally expect a high standard of quality.
2. Warranty Protection
If your vehicle is still under warranty, using non-genuine(OEM) parts can be risky. Should something go wrong, the automaker or dealer might refuse warranty coverage, since they can’t be sure whether the issue was caused by the use of non-OEM parts.
3. Fewer Mistakes
OEM parts are made specifically for your vehicle model. As long as you confirm the OEM part number, you’re unlikely to end up with the wrong part. This saves both time and labor costs.
4. Maintaining Original Performance
OEM parts are guaranteed to match the specifications your car was designed for—fuel efficiency, acceleration, air conditioning performance, and more. So, when you replace a part with an OEM equivalent, you can expect the same performance as when the car was new.
Disadvantages of OEM Part
1. Price
OEM parts are usually quite expensive. In general, aftermarket parts cost about 50% to 70% of what OEM parts do. That’s why many consumers still prefer aftermarket parts. Also, the high cost of repairs for many vehicles is often a reflection of the expensive OEM parts.
2. Limited Availability
As mentioned earlier, for many car brands, you can’t simply walk into a dealer or service center and buy parts. Consumers are often left out. Even though some brands now offer online purchasing, not all automakers provide this option.
3. Discontinued Production
Automakers don’t supply OEM parts forever. Most brands stop offering OEM parts about 15 years after a model ends production, so you may run into “sold out” situations.
4. No Individual Replacement
Many OEM parts are now sold only as assemblies. This means consumers might be forced to buy components that haven’t actually failed.
5. Original Performance Isn’t Always Perfect
While OEM parts are meant to maintain your car’s original performance, automakers aren’t immune to design flaws. In those cases, replacing a problematic part with another OEM part might not solve the issue. Sometimes this is a serious problem, though with some brands, it rarely happens. So, it’s hard to generalize.
What Are Aftermarket Parts?
Once you understand what OEM parts are, aftermarket parts become pretty easy to grasp. Anything that isn’t OEM is considered an aftermarket part. However, aftermarket parts can actually be divided into two main categories: OE-style aftermarket parts and performance or modified aftermarket parts. We’ll break down each type below.
What Are OE-Style Aftermarket Parts?
Purpose
OE-style aftermarket parts are components made by third-party manufacturers to match or closely resemble OEM parts. Their size, specifications, and performance are usually very similar—or sometimes identical—to OEM parts. Whether they’re just similar or truly identical depends on the capabilities and strategies of the manufacturer. The main purpose of OE-style aftermarket parts is to serve as a replacement for OEM parts, mainly because OEM parts are often quite expensive.
Price Range
Typically, OE-style aftermarket parts cost about 50%–70% of what OEM parts do. In some cases, you might even find aftermarket parts priced at just 10%–20% of the OEM equivalent. However, you need to be very careful with these ultra-cheap options—they often come from factories in places like China, India, or Africa, where quality control may not be as rigorous.
Risks and Considerations
If these parts are for things like seat covers or accessories, the risk might not be too high. However, if you’re dealing with critical components like engine or transmission parts, using low-quality OE-style aftermarket parts could lead to serious safety concerns.
OEM Companies Also Sell OE-Style Aftermarket Parts
As mentioned earlier, some OEM companies also sell OE-style aftermarket parts under their own brand. For example, shock absorber manufacturers like Bilstein and KYB are OEM suppliers for many car brands. In addition to supplying shocks to automakers, these companies also offer the same/similar models to the public as aftermarket products.
The main difference is that when these OEM companies sell these shocks directly, they don’t carry the automaker’s logo. In other words, these parts haven’t been certified by the car brand, even though they’re made by the same company and may be identical to the genuine part. As a result, they’re still considered OE-style aftermarket parts.
OE-Style Aftermarket Parts Advantages
1. Price
Compared to genuine or OEM parts, price is definitely the biggest draw of OE-style aftermarket parts. You can get products with nearly the same performance as genuine or OEM parts, but at a much more affordable price.
2. Easy to Find
OE-style aftermarket parts are widely available. All you need to do is visit a distributor or search online for your car model—there are basically no restrictions on purchasing.
3. Availability for Older Models
Genuine or OEM parts are usually only guaranteed to be available for about 15 years. After that, owners may not be able to buy those parts anymore. However, there will almost always be a factory producing aftermarket parts, so you generally don’t have to worry about parts being discontinuedˋ.
4. Wide Range of Brands
There are many aftermarket brands to choose from, so you can pick the one that best suits your preferences.
Disadvantages of OE-Style Aftermarket Parts
1. Risk of Buying the Wrong Part
It’s often unclear which genuine or OEM part a third-party manufacturer used as the basis for their OE-style aftermarket part. Depending on the type of part, the process of confirming compatibility can become quite complicated.
2. Quality Uncertainty
As mentioned earlier, there are many types of OE-style aftermarket parts, and it’s often hard to know exactly which factory produced them. Sometimes, even OEM companies may outsource production to other factories. That’s why it’s crucial to carefully choose reputable brands. For important components—like suspension arms—it’s best to avoid extremely low-priced products from Amazon or Ebay, as poor quality can pose serious safety risks.
What Are Performance/Modified Aftermarket Parts?
This is a completely different field. Many people feel their car isn’t perfect after buying it. Sometimes the power isn’t enough, or the wheels, chassis, and brakes don’t meet the owner’s expectations. As a result, car enthusiasts will try to modify their vehicles, upgrading to stronger parts. These parts are also classified as aftermarket parts.
Currently, the most common types of modified aftermarket parts include larger wheels, more powerful shock absorbers, bigger turbos, and enhanced cooling components.
There are many brands offering these strengthened parts. Some factories develop their own products, while many performance parts actually come from OEM companies. For example, OEMs like KYB, Bilstein, and Akebono also offer strengthened parts specifically for modified cars.
However, it’s important to note that in this field, price markups are a serious issue, and there are simply too many brands for consumers and modification shops to choose from. If the technician handling the modification isn’t professional enough, your car’s performance might actually get worse. The most obvious example is the big brake kit. Theoretically, a big brake kit will not necessarily shorten stopping distance, but we often see people claiming their braking improved after installing one. Many technicians, car enthusiasts, and even some manufacturers of these strengthened aftermarket parts don’t always understand vehicle engineering. Blindly installing larger or stronger parts can easily disrupt the car’s original balance and end up wasting money.
Advantage of Performance/Modified Aftermarket Parts
Better Performance
With the right modifications, better performance is possible. You can achieve results that surpass the original factory specifications, enhancing handling, power, braking, suspension, and more.
Disadvantages of Performance/Modified Aftermarket Parts
1. Legality
In some countries or regions, vehicle modifications are illegal. Installing performance or modified aftermarket parts may violate local laws or emission standards, potentially resulting in fines or failed inspections.
2. Price
Performance/modified aftermarket parts are often very expensive—sometimes costing twice as much as OEM or genuine parts, and usually over $1,000. However, the performance gains rarely match the price increase.
3. Poor Resale Value
In the used car market, buyers typically won’t pay more for a car just because it has expensive aftermarket parts. On the contrary, people may suspect the car has been driven hard or abused, leading to a lower overall valuation.
4. Quality Risks
Just like OE-style aftermarket parts, performance/modified parts are not certified by the automaker, so there’s always some risk involved. A higher price doesn’t necessarily guarantee better quality.
5. Knowledge Required
Incorrect modifications can actually reduce performance or compromise vehicle balance, sometimes even affecting safety. If the owner lacks sufficient knowledge, finding a trustworthy and professional modification shop becomes essential. However, learning about these upgrades and finding a reputable shop both require extra time and money.
Conclusion
In this article, TGQ has provided a detailed explanation of the differences between OEM parts and aftermarket parts, hoping to give readers a clearer understanding of their options when it comes to car components. So, when it’s time to replace a part, should you choose OE parts or aftermarket parts? As mentioned in the article, for critical components that impact safety, OEM parts are generally recommended. However, what exactly qualifies as an “critical” part? The answer can vary from person to person.
TGQ as a manufacturer of OEM (genuine) parts, OE-style aftermarket parts, and performance aftermarket parts. TGQ can’t definitively tell you which type is best for your situation (doing so would put us in an awkward position). Ultimately, it’s up to each car owner to carefully consider their own needs and make the best choice for their vehicle.
Reference
- T.G.Q R&D
- T.G.Q Sales
