Most laymen have an incorrect thought that OEM parts are always better than aftermarket parts. From technical sight, OEM parts are often better.

We know that OEM automotive parts are offered by the vehicle manufacturer. They have obvious virtue:

  1. OEM parts are built by companies that specialize in auto parts manufacturing like Visteon, Bosch, Delphi, Aisin, etc., and someitmes even the auto manufacturer themselves. All of these companies are big-time multinationals who trade on their good name.
  2. They're built to the OEM's specs, which were created to ensure worry-free operation for the length of a new car warranty. After-market parts aren't always manufactured to the OEM's spec, and thus can fail faster (or cause a failure in related parts).
  3. OEM parts are *never* made by fly-by-night manufacturers who just decided to start manufacturing auto parts 6 months ago. After-market parts, on the other hand, can sometimes be sourced from companies that will make shocks one week and children's toys the next.

Otherwise, aftermarket parts are made to increase performance and make a vehicle look better, they made of expensive composite materials to weight less and be more functional, for instance: H-beam connecting rods made by maxspeedingrods are forged by 4310 EN24 steel for the highest strength and durability, dedicated for Racing. Therefore, there are some after-market parts that are substantially better than OEM parts.

Of course, there are some after-market engine parts that are virtually identical to OEM parts. This is because the companies selling the after-market parts are the same supplier that makes the OEM part for the automaker...if you buy a Bosch spark plug, for example, you might have a hard time spotting the difference between the Bosch plug and a plug that comes directly from the dealership's parts counter.

Additionally, there are some examples of after-market parts that are substantially better than OEM parts. Shocks are a great example: OEM shocks are usually mediocre, while a premium after-market shock from someone like King Shock Technology or Bilstein is excellent.

Still, if you have to choose between parts and don't know which is truly best, my advice is:

  • You can't go wrong with OEM
  • You get what you pay for - OEM parts and premium after-market brands are generally more expensive for a reason
  • Name-brands are always best

If you're going to buy after-market, make sure they're clearly a premium brand.