If you've ever been in the market for new parts for your vehicle, you'll have likely seen the OEM and OES abbreviations at some point. When a buyer is looking for the most reliable part or value-friendly part, it can be frustrating that these abbreviations are not particularly friendly to the average consumer, especially when the definitions are so similar. Nonetheless, if you're looking for a car part, it is helpful to understand the meanings behind the codes and lingo.
For starters, OES stands for Original Equipment Supplier, while OEM stands for Original Equipment Manufacturer. Many of the parts you'll come across will fit one of these categories. People are sometimes confused because the definitions themselves are actually so similar. Put simply, an Original Equipment Supplier part is made by the manufacturer who made the original factory part for your vehicle model. On the other hand, an Original Equipment Manufacturer may not have made that specific part for your vehicle originally, but has an official contract history with the automaker.
Say for instance that your car's manufacturer contracts Company A and Company B for a certain part. If your vehicle originally came equipped with Company A's part, another Company A part would be considered OES, while Company B's part (however identical) would be OEM. Automakers tend to outsource the manufacture of a given part to multiple companies for numerous reasons. With more than one company making the same identical part, an automaker can ensure steady production without the risk of being held up by contractual disagreements.
It's important to underline the fact that OEM and OES parts are typically indistinguishable from one another when it comes to function and performance. Even if it may be a different manufacturer from one part to another, they're all following the exact specifications outlined by the vehicle's designer.
With that said, some consumers are tripped up by the fact that two of the same parts may have aesthetic differences. Although the appearance of one OEM part will never be too different from another, there may be a few different reasons for this change. For example, one manufacturer may have a patented numbering system that sets their parts apart; this has been the case for Porsche and some other manufacturers. The superficial design choices may be at the manufacturer's discretion. So long as a manufacturer has been endorsed by the automaker however, you can rest assured that the new part will work otherwise identically to its predecessor.
The rules change when you get into the field of aftermarket parts, however. These parts are so-named because they either stem from manufacturers or designs that never came with an original sale of the vehicle, and are therefore purchased independently after the fact. These "third-party" parts open up the market significantly, and are generally geared towards vehicle owners who want to forego the standard (but expensive) official licensed parts for an unofficial alternative.
Aftermarket parts have a much wider range of prices and qualities. Although purchasing these parts can help you elude the branding costs of a OEM component, the unregulated nature of aftermarket components means you'll need to have a cynical eye when shopping around. Some parts (referred to as "counterfeit parts") are usually very attractively priced, but have a pitifully low quality to match. Counterfeit part manufacturers tend to go out of their way to make their components look as close to the real thing as possible, sometimes making it difficult to tell the gold from the garbage. As a general rule, if a price seems too good to be true, it almost certainly is.
On the other hand, aftermarket parts sometimes even offer a technically superior alternative to the official parts. Whether a prime aftermarket part is made of materials that would have been too costly to mass-produce, or simply better designed, these parts are perfect for an experienced home mechanic who wants to optimize their vehicle. Better still, many of these enhanced aftermarket parts include a lifetime warranty from their manufacturer; this is particularly helpful considering replacing official OEM parts with third-party sources can void parts of your original warranty.
The proper choice of part type ultimately depends on the needs of the car owner. As a general rule, purchasing the official licensed parts is safe, but with such high prices associated with the branding, it may be worth it to strike out on your own for aftermarket parts. If you're still unsure, you can talk to a mechanic, or reach out to a YourMechanic representative to help you.