OEM stands for Original Equipment Manufacturer, plain and simple. It means that these parts will be the same ones that your vehicle was originally made with. However, that doesn’t always mean that they will be BMW Genuine Parts. Those parts are specifically made by BMW and typically include things like the trim, exterior body parts or electrical wiring. OEM parts are not always made by BMW – sometimes the company, as many other car manufacturers do, contract out the design to a suitable manufacturer to produce it with BMW design specifications and quality requirements. The good news is, with OEM parts, you can get the same part that your vehicle was made with, giving you peace of mind.
In general, OEM parts come with an included warranty and have been thoroughly tested for performance. Since they were the parts in your vehicle when it first rolled off the assembly line, they’ll fit and perform exactly the same as the old parts did. Be careful when shopping for parts that are labeled as “OEM Quality” or “Meets or Exceeds OEM Standards” because it doesn’t actually mean they were produced by BMW contractors.
When you take your vehicle for a repair at the dealership, they will recommend OEM parts because they keep them in stock and they know they are of good quality, because contractors that BMW trusted produced the parts in the first place when the vehicle was put together.
Aftermarket parts are parts that have been produced outside of a production contract with BMW. There are thousands of companies that produce aftermarket parts – everything from brake pads to mufflers to alternators and batteries. They are generally less expensive than OEM parts, and how much you save will vary by brand.
Sometimes, the quality of an aftermarket part can be as good as OEM or even better than it, depending on the particular manufacturer. Some aftermarket companies reverse-engineer BMW parts and improve upon its weaknesses. The availability and number of aftermarket parts is also greater than OEM – you can walk into any auto parts shop or mechanic and they’re bound to have the correct part that fits your vehicle. Having more choices makes it easier for you to shop around to find the best deal and the best quality, so you can customize your vehicle the way you prefer. If you find the selection overwhelming, however, consult with a trusted mechanic or simply just stick with the OEM part if the price difference isn’t significant.
Always purchase from aftermarket brands that you trust or ones that have been recommended to you by your mechanic. There are a many parts out there of inferior quality, and even something simple like a brake pad can be of poorer quality if it wasn’t thoroughly heat tested, for example.
When in doubt, it’s always a safe bet to go with OEM parts. There’s no question to their quality or availability at the dealership and most of them come with a warranty, so if anything were to go wrong, the dealership would replace it at no cost to you.