Reading an OEM number: format, location, pitfalls
"Front bumper, Golf" returns twenty parts. 5Q0 807 221 A returns one — provided you kept the A.
In short
An OEM number is the reference the vehicle manufacturer assigns to one exact version of a part. It is stamped, etched or printed on the part itself, retrievable from the brand catalogue via the VIN, and readable in blocks that differ per brand group. The trailing letter or suffix is not decoration: it is usually the only thing separating two versions that look identical.
What is an OEM number?
OEM stands for Original Equipment Manufacturer. The OEM number is the reference the car manufacturer itself assigns to a part, listed in its own parts catalogue. Every version, every facelift and every engine variant can have its own number — which is exactly why it's so precise.
Alongside the OEM number, aftermarket references also exist: the number an independent manufacturer or supplier assigns to a comparable part. These numbers differ by brand and aren't interchangeable with one another. The OEM number remains the only number that means the same thing across every source.
Where to find the OEM number
- On the part itself: cast, etched or on a sticker — usually on the back or on a mounting flange.
- Via the chassis number (VIN): this lets the brand's catalogue pull up the exact version fitted to your car.
- In the electronic parts catalogue (EPC) of the brand or your parts supplier.
- On the original invoice or delivery note from a previously ordered part.
- In a dismantling file: note the number down before the part comes out of the car.
What an OEM number looks like
| Brand group | Typical format | Point to watch |
|---|---|---|
| VAG (VW, Audi, Seat, Škoda) | 3 digits – 3 digits – 3 digits + letter, e.g. 5Q0 807 221 A | The trailing letter indicates the version and matters. |
| BMW / MINI | 11 digits in groups, e.g. 51 11 7 260 953 | Spaces are often dropped; the number stays the same. |
| PSA / Stellantis | 10 characters, often starting with digits, e.g. 9678440380 | Several valid numbers can sometimes exist for identical parts. |
| Toyota / Lexus | 5 – 5 – 2 digits, e.g. 52119-02A90 | The final block refers to version or market. |
| Mercedes-Benz | A + 10 digits, e.g. A2058850058 | The letter A is part of the number, don't drop it. |
Why searching by number works better
A search by description — "front bumper Golf" — returns parts from different generations, with or without parking sensors, with or without washer jets. A search by OEM number rules all of that out. For a body shop, that's the difference between one delivery and two returns.
- Fewer wrong deliveries, and so less downtime in the workshop.
- Faster comparison between suppliers, since you know for certain it's the same part.
- A traceable file: the number appears on the quote, the order and the invoice.
Searching by OEM number via Ottroo
With a single OEM number, Ottroo queries several sources at once: dormant stock at fellow businesses, specialised platforms for used and refurbished parts, and dismantlers. Results start locally and expand to region, Benelux and Europe, each time showing condition, origin and distance.
Cross-referencing: one part, several numbers
An original part rarely carries a single number. The manufacturer uses its OEM reference, the original supplier often runs its own manufacturer number, and aftermarket producers add a catalogue number of their own. Searching only the number printed on your invoice therefore means missing part of the market every time.
Cross-referencing maps those numbers onto each other. Using your OEM number, Ottroo queries every connected source at once and also surfaces results listed under an equivalent number — at peer businesses, on specialist platforms and at dismantlers. If a supplier only knows the aftermarket reference, their part still appears in your results.
In practice: record the OEM number before the old part comes off the vehicle, and keep the trailing letter or suffix when trim levels differ. That final character is often the only thing separating two otherwise identical versions.
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Frequently asked questions
What is the OEM number of my car?
The OEM number is the reference the car manufacturer assigns to a specific part of your car. It's unique per version and appears in the brand's official parts catalogue.
Where do I find the OEM number of a part?
Usually on the part itself — cast, etched or on a sticker. If you can't find it there, retrieve it via the chassis number in the brand's parts catalogue or through your parts supplier.
Is an OEM number the same as an aftermarket number?
No. The OEM number comes from the car manufacturer; an aftermarket number comes from an independent manufacturer. They may refer to a comparable part, but they aren't interchangeable as references.
Can I use an OEM number to find reused parts too?
Yes. Reused original parts carry the same OEM number they had when new. That's why the number is the fastest way to line up new, reused and refurbished offers side by side.
How do I look a part up by OEM number?
Take the number from the part itself, from the manufacturer's catalogue or via the VIN, and enter it as your search term. Ottroo then queries peer stock, specialist platforms and dismantlers at once, and also surfaces listings recorded under an equivalent number.
What is the difference between an OEM number and an aftermarket number?
An OEM number comes from the vehicle manufacturer and means the same thing across every source. An aftermarket number is an independent manufacturer's own reference and differs by brand. Searching by OEM therefore returns the most complete and reliable result.
Why does the letter at the end of a VAG number matter so much?
On a number like 5Q0 807 221 A, that final letter marks the revision or the trim version. Drop it and you are searching a family of parts rather than the one that fits; keep it and a bumper for a car with parking sensors stops being confused with the one without.
The number is unreadable on the old part. What now?
Go via the VIN. The brand's electronic parts catalogue resolves the chassis number to the exact build, including the version of the part fitted at the factory, which is more reliable than reading a corroded stamping with a torch.
Two suppliers quote different numbers for what looks like the same part. Who is right?
Often both. One is quoting the OEM reference, the other the original supplier's own manufacturer number or an aftermarket catalogue number. Cross-referencing maps them onto each other, which is why searching one number can still surface a listing recorded under the other.
Search by number, across every source at once
With a single OEM number, Ottroo queries the stock of fellow businesses, specialised platforms and dismantlers.