Buying a spare part online can be fast and cheap – but only if you purchase exactly the component that fits your vehicle. The most common mistake is ordering a part by car model alone. On modern vehicles, suppliers, engine variants, and small design details can change within a single model year. The reliable way to avoid a misfire is to work with the VIN code and the OEM number of the part. In this guide, we will walk through it step by step.
What the VIN is and why it matters
The VIN (Vehicle Identification Number) is a 17-character identifier for your vehicle. You will find it in the registration document, on a sticker in the driver's door frame, under the windshield, or on a fixed part of the body. The VIN carries information about the manufacturer, model, year of production, engine type, and often the specific equipment level.
Thanks to the VIN, a seller or parts catalogue can determine exactly which variant of a component your car needs. Two seemingly identical cars of the same model may have different brake calipers, alternators, or headlights – and the VIN reveals these differences.
What the OEM number is and how to use it
The OEM number (Original Equipment Manufacturer) is the original catalogue number of the part assigned by the carmaker. It is the most precise identifier of a specific component. Unlike a generic name such as "front shock absorber," the OEM number is unambiguous – it corresponds to exactly one part.
- Where to find the OEM number: directly on the old part (stamped or on a label), in the service documentation, or in an online catalogue searched by VIN.
- What it is for: it lets you locate the original part as well as a high-quality alternative in OEM quality at a lower price.
- Watch the cross-references: one OEM number can have several equivalents from different brands (TRW, Bosch, Sachs). These cross-reference tables are your best friend.
Step-by-step procedure
1. Copy the VIN exactly
Do not confuse a zero with the letter O, or a one with an I. A single typo leads to the wrong result. We recommend copying the VIN from the registration document and comparing it with the plate on the vehicle.
2. Identify the part's OEM number
The safest approach is to remove the old part and copy the number from it. If that is not possible, use the VIN in an online catalogue that shows you a diagram with the OEM numbers of individual components.
3. Verify compatibility
Before ordering, check that the offered part lists your engine (engine code), year of production, and where relevant the VIN range. For parts such as brakes, the disc diameter or the type of braking system also matters.
4. Compare original and alternative
For many parts you can save money by choosing a quality aftermarket option with identical parameters. Always compare the OEM reference, however, so that the connector shape, number of pins, and dimensions all match.
Common mistakes to avoid
- Ordering by model name alone without checking the engine variant.
- Ignoring the VIN range on facelifted versions.
- Mixing up the left and right side on paired parts, such as headlights.
- Overlooking the connector type on electrical components.
How parts4cars.cz helps you
At parts4cars.cz we specialise in quality spare parts imported from Germany. We list OEM references and cross-reference tables with our parts, so you can easily confirm the match with your vehicle. If you are unsure, simply send us your VIN and we will confirm compatibility before you order. That way you avoid unnecessary returns and the hassle of fitting the wrong part.
Working with the VIN and OEM number takes a few extra minutes, but saves hours and money. When the part fits on the first try, you save on shipping, time in the workshop, and stress. And that is exactly our goal.