If you are fairly new to the wonderful world of DIY maintenance and upgrades on your car, you’re probably a bit overwhelmed with all the acronyms, like DIY (do it yourself, if you didn’t know.) These acronyms, like DCT, LSD, ASC, and the alphabet soup of other shorthand signifiers are pretty easy to google and find a quick answer. There are a few common acronyms that don’t have the most uniform definitions, though. OE and OEM are two specific acronyms that we regularly see used interchangeably, but that isn’t quite right. We’re going to clear this up for you here and now.


A Genuine, or OE, part is the exact part made by the exact company that your vehicle manufacturer used during the original assembly of your car.

You have likely seen some parts listed as ‘OE’ or ‘OEM’ and thought ‘that’s the same thing, right?’ Well, sort of. OE stands for ‘Original Equipment.’ This is the exact part used by the vehicle manufacturer in the production of your specific car and is branded as such. So, if you found an ‘OE’ water pump, that is the exact water pump used by, let’s say BMW when they built their car. It is branded with the vehicle manufacturer’s name and what you would receive from the parts counter at your local dealer for a hefty price.


An OEM part is the same exact part that was used during the original assembly of your car, but branded with the part manufacturer’s name.

That brings us to ‘Original Equipment Manufacturer.’ This is the part manufacturer’s branded version of the exact same part used in the production of your car. It is the same as the OE part but isn’t branded with ‘Genuine BMW’ or whatever brand of car you have. So, for a fraction of the price, you are buying exactly the same part, just branded with ‘Bosch’ or whoever the part manufacturer is. 


An aftermarket replacement was not used during the original assembly of your car, but is a direct replacement by a third-party company. It doesn’t inherently mean ‘better’ or ‘worse,’ it just means different than the original.

Finally, we have ‘aftermarket’ parts. These are companies who are not OEM suppliers for any vehicle manufacturer, but still produce replacement parts. It’s quite common that folks assume aftermarket means it’s a performance upgrade. However, it is actually just a manufacturer of that part, like the water pump, who did not originally supply that part for the vehicle manufacturer. Basically, these are the replacement parts you find for generally lower cost and are usually perfectly fine to use, but are not made by the company who produced the part originally for that vehicle manufacturer.


So, Original Equipment (OE) is the Genuine part. It’s still made by ‘Bosch’ or whoever, but it is branded as the Audi, BMW, Volkswagen, Porsche, MINI, or Mercedes Benz part. Original Equipment Manufacturer (OEM) is the exact same part, just branded by the part manufacturer, not the car company. So the part may say ‘Bosch’ rather than ‘BMW.’ Lastly, an aftermarket part is just a replacement part that was not used by BMW (or whatever vehicle company) when they originally built the car. Make sense?