How to Find the Right Car Part for Your Vehicle

To find the right car part, begin with the year, make and model, then narrow the match by trim, engine, drive type, body style and production date. Before you order, confirm the result in the fitment table and compare it with the number and shape of the part you are replacing. Many models share a name but use different parts underneath, so one missed detail can mean the wrong part arrives. This guide covers the details to collect, where to find them on the car, how to read an old part, how OEM and aftermarket numbers relate, and how to use a fitment table.

The Vehicle Details That Decide Fitment

A single model year can come with several engines, trims and brake or suspension packages. Each of those can change which part fits. Write the details below down once and keep them on your phone, because you will need them every time you shop for parts.

• Year, make and model, for example a 2018 Ford F-150
• Trim level, such as XL, XLT or Lariat, which can change brakes, lighting and electronics
• Engine size, cylinder count, fuel type and engine code if you can find it
• Drive type: front-wheel drive, rear-wheel drive, 4WD or AWD
• Body style, door count, and cab and bed configuration on trucks
• Production month and year from the door label
• The full 17-character VIN

Where to Find Each Detail on Your Car

The VIN appears on the lower driver-side corner of the windshield, on the driver door jamb label, and on your title, registration and insurance card. The certification label on the driver door jamb also shows the production month and year, which is the date that matters when a part changed partway through a model year.

Engine details are usually printed on the emissions label under the hood and in your owner's manual. Trim and body style can come from the window sticker, your title or service records. If the car has a lift kit, an engine swap or other changes, note them too, because catalog data describes the vehicle as it left the factory.

Why Production Date and VIN Matter

Automakers sometimes change a part in the middle of a model year. Catalogs show this with notes like built before or built after a certain date, or early and late versions. Your model year alone cannot tell you which one you have, but the build date on the door label can.

The VIN encodes the manufacturer, model, engine and plant, and the free NHTSA decoder will read it for you. It is very useful, but a VIN does not reveal every factory option. Some option-dependent parts, such as certain modules and trim pieces, may still need a dealer parts lookup or the build sheet.

Reading the Number on the Old Part

The part you are removing is good evidence of what fits, as long as you read it carefully. Clean it gently so you do not wipe away markings, and photograph it in place before removal so you can see connectors, hoses and orientation later.

• Record every number, including prefixes, suffixes and revision letters
• Do not assume the largest number is the part number; it may be a casting or batch number
• Compare connector shape and pin count
• Compare mounting hole positions, overall size and thread size
• Check left or right, front or rear, and upper or lower position
• Remember a previous owner may have installed a part that was wrong

OEM, Supplier and Aftermarket Numbers

An OEM number is the vehicle manufacturer's own catalog number. It can be superseded, meaning a newer number officially replaces it, and that newer number is still correct when the catalog lists it as the replacement. Aftermarket brands use their own numbers and publish interchange lists that tie them back to one or more OEM numbers.

Treat an interchange as a strong lead, not the final word. Check the application notes and specifications that come with the part. Be wary of any listing that says it fits many vehicles but gives no fitment table, no specifications and no clear quantity.

Using a Fitment Table Before You Buy

Every part page has a fitment table listing years, trims, body styles and engines. Read it row by row against your notes, and pay attention to footnotes such as with heavy-duty brakes, with electronic parking brake or with power-folding mirrors. If a part needs your VIN or has two rows that both seem to match, stop and confirm before ordering. Our fitment help page explains how to read each column.

Brakes are a good example. On brake rotors the rotor diameter and brake package matter as much as the year, so a Chevrolet Tahoe brake rotor listing may show several sizes for one model year. For an alternator, match the engine and amperage, and on a truck such as the F250 Super Duty alternator check for dual-alternator or heavy-duty packages. A replacement mirror adds side, power, heat, turn signal and towing features, which is why Ford F150 mirrors come in many versions for the same year.