OEM parts are made for, and approved by, the original equipment manufacturer, the company that built the vehicle or machine. Aftermarket parts are made by other suppliers to fit and do the same job, but without that maker's approval.
Both can be good. The difference lies in who controls the drawing, who approves the part and who carries the risk if it fails.
How the terms are used
- An OEM part is supplied to the vehicle maker for its production line or its own branded spares.
- An OES part, or original equipment supplier part, is the same part made by the same supplier but sold in its own packaging.
- An aftermarket part is made by a third party, usually from a sample or reverse-engineered drawing.
- Some sellers say "OEM quality" to mean a part made to the same specification. That is a claim, not an approval.
How the supply chains differ
OEM supply runs on the vehicle maker's drawing, which shows materials, tolerances and tests. The supplier must pass a formal approval, usually a PPAP, before shipping. Changes to process or material need the customer's written approval.
Aftermarket supply runs on the importer's own specification. Often there is no drawing at the start. The supplier measures a genuine part and makes a drawing from it. That process, and its legal limits, is covered in reverse-engineering a part.
In the aftermarket you set the quality bar yourself. If your specification is loose, the part may fit at first but wear faster or fail in service.
Volumes differ too. OEM orders are scheduled months ahead and called off weekly. Aftermarket orders are smaller, cover many part numbers and arrive less often, so suppliers plan them differently.
Legal points to watch
Do not use a vehicle maker's trade mark on your packaging or part. Part numbers can usually be quoted for cross-reference, but rules differ by market. Some designs are also protected by design rights or patents.
Some parts are regulated. Brake parts, lighting and some safety items need type approval or test marks in many markets. Check with your regulator or a specialist adviser before you import.
What this means when you source from India
- If you need OEM-grade supply, choose a plant with IATF 16949 and PPAP experience.
- If you sell aftermarket parts, write a full specification with material, hardness, critical dimensions and tests.
- Ask for samples measured against a genuine part, with a dimensional report.
- Agree how the part is marked so it does not infringe a vehicle maker's rights.
- Keep test records for each lot, because your customers may ask for them after a failure.
Next step
We help you write the specification, find the right plant and check samples against a genuine part. Book a free sourcing review to start.