How to find the correct part number – identifying the right spare part

When looking for used car parts, many customers ask the same question: How do I know if a spare part really fits my vehicle? The answer is simple: the part number.

This article explains what a part number is, where to find it, and why it is essential when buying used auto parts.

What is a part number?

A part number (often called an OEM number) is a unique identifier assigned by the vehicle manufacturer. It ensures that a component is designed for specific models, engines, or production years.

Note: Parts may look identical but still have different part numbers – and may not be compatible.

Why is the part number so important for used parts?

Used parts require special attention because vehicles change technically over time, facelifts and engine variants exist, and small differences can affect compatibility.

Result: The part number prevents wrong purchases and unnecessary returns.

Where can you find the part number?

1. On the part itself

Many parts have the number engraved, stamped, or printed on a label.

• Headlights
• Control units (ECUs)
• Engine and transmission parts
• Body parts

2. In service records or invoices

Workshop invoices often list OEM part numbers and manufacturer references.

3. Using the Vehicle Identification Number (VIN)

The VIN is the most reliable way to identify the correct part. It allows professionals to determine the exact vehicle configuration and all compatible spare parts.

You can typically find the VIN in the registration documents, in the engine bay, or at the base of the windshield.

4. Through a professional auto recycler

Specialists like Kempers can identify the correct part using the VIN, engine code, and transmission code.

OEM number vs. manufacturer number

• OEM number: original vehicle manufacturer number
• Manufacturer number: number from the part supplier (e.g. Bosch, Valeo)

Both can refer to the same component but are not identical.

Common mistakes when identifying parts

• Searching only by model year
• Comparing photos only
• Assuming “it fits a similar model”
• Ignoring engine or transmission codes

Rule of thumb: The part number is more reliable than looks or descriptions.

Conclusion

If you want to make sure a spare part fits your vehicle, the part number is essential – especially for used parts. It saves time, money, and unnecessary frustration.