An OEM number identifies a part in a manufacturer's catalogue at a point in time. It does not, on its own, identify what fits a specific vehicle — which is why quotations based on a number alone produce wrong deliveries at a rate that surprises new importers.
What an OEM number is and is not
The number is the vehicle manufacturer's internal part reference. It is authoritative and it is also unstable in three ways.
Supersession. Manufacturers revise parts and replace numbers. Part A is superseded by part B, which is later superseded by part C. All three may still be in circulation. A supplier quoting the current number and a supplier quoting the original number may be offering the same physical component — or the revised design, which may differ dimensionally.
Regional variation. The same model built for different markets frequently uses different parts, with different numbers, driven by emissions, climate or local regulation.
Mid-production change. Manufacturers change parts partway through a model year. Two vehicles of the same model year, built four months apart, can require different components. This is the single most common cause of a part that matches on paper and does not fit.
The seven fields
Send these together and a quotation becomes reliable:
- OEM number, exactly as it appears, including spaces and separators
- Vehicle make, model and year
- Engine code — not displacement. A 2.0-litre engine may exist in four variants with different components
- VIN where available — this resolves nearly every ambiguity, since it encodes plant, production date and specification
- Production date if no VIN, month and year, which handles mid-production changes
- Position — front/rear, left/right, upper/lower, inner/outer. Specify by vehicle orientation and state the convention you are using
- Photographs of the actual part, including any markings cast or printed on it
Photographs resolve cases where numbers cannot. A part removed from the vehicle, photographed from several angles with its markings legible, settles identification more reliably than a catalogue lookup.
Aftermarket cross-references
Aftermarket manufacturers assign their own numbers and publish cross-reference tables to OEM numbers. These are useful and imperfect.
Cross-references are compiled by the aftermarket manufacturer and reflect their judgement about equivalence. A part cross-referenced to an OEM number may differ in material, tolerance, or a mounting detail that matters. Where several OEM numbers cross to one aftermarket number, the aftermarket part is designed to cover a range — which usually works, and occasionally does not for a specific variant.
For a first order of any part, confirm against the physical component rather than the table. Ask the supplier for dimensioned photographs of the part they intend to ship, and compare against your own measurements of the part being replaced.
Quality tiers
The same OEM number can be quoted at prices differing by a factor of five, and the range is real rather than negotiating noise.
Genuine parts come in vehicle manufacturer packaging. OE-supplier parts are made by the company that supplies the vehicle manufacturer, in their own packaging — frequently the same production line, at a substantially lower price, and the best value in the range for most applications. Aftermarket branded parts come from independent manufacturers, spanning a wide quality range. Unbranded parts vary enormously and require inspection.
When comparing quotations, establish which tier each supplier is quoting before comparing prices. A quotation that does not state the tier is not comparable to one that does.
What to confirm before a bulk order
Ask for the physical part markings on the item to be shipped, packaging photographs, the material or specification where it affects performance, and the applicable certification for your market.
For safety-critical components — braking, steering, suspension, airbags, lighting — certification is a market-access requirement, not an optional extra. Requirements differ by market and cover both the part and its marking. Importing without the applicable approval risks seizure and, more seriously, liability.
Order a sample of every part number on a first order. For a multi-SKU order this feels laborious and it catches the mismatches while they are still cheap to fix.
Sending a multi-SKU enquiry
Send a spreadsheet, one row per part, with columns for the seven fields plus target quantity, quality tier and packaging requirement. A structured list gets a structured quotation with a line per part; an unstructured email gets partial answers and a follow-up thread.
Send us your list and we will confirm what we can identify with confidence, flag which lines need a VIN or a photograph to resolve, and quote by tier so you can see what you are comparing.