Car part numbers explained: why they decide whether your stock is found

Every part has a number from whoever made it. A genuine part carries the carmaker's number, such as Toyota's 04152-YZZA1 for an oil filter element. A part made by a supplier to the carmaker, or by an aftermarket maker, carries that company's own number as well, such as NGK's BKR6E spark plug. The two numbers describe the same job on the car in different catalogues.

Shops often add a third number of their own: an internal code, a shelf location or a stock code. Those are useful to you but meaningless to a customer or a catalogue. In a stock list, the part number column should always hold the maker's number, with your own code in a column of its own.

A fourth kind of number turns up on older stock: a carmaker's number that has since been replaced. It is still a real number, it is still printed on the box, and customers still read it off the label of the part they are replacing. It belongs in your list as much as the newer one does, for reasons the section on supersessions sets out.

Customers describe parts; they rarely quote them. Of the 1,380 requests that reached Easy Auto through the website and the first WhatsApp bot between 20 July and 1 November 2026, 67 carried a part number. Every other one had to be turned into a number before any stock list could be searched, and that work is ours, not yours.

A customer writes "oil filter for a 2017 Camry" or sends a photo of the old filter. Before any list is searched, Easy Auto works out the carmaker's number for that car, from its details, its VIN where we have it, the label in the photo, and catalogue data. That number is then looked for in every list we hold, in two places: as the part number of a genuine line, and in the genuine-number column of OE-brand and aftermarket lines.

So an aftermarket line without a cross-reference can only be found by someone who already asks for the aftermarket number, which almost no customer does. Of the 304 part lines customers sent Easy Auto on WhatsApp between 7 October and 2 November 2026, 10 were matched to a list we hold. Cross-references are one of the things that would raise that number. When no list holds a part, our sourcing desk asks suppliers one part at a time by WhatsApp or phone, which is slower for the customer and costs every supplier asked a reply.

A cross-reference is a claim, made by the maker of a part, that the part does the job of a given carmaker's number. In a stock list it sits in the genuine-number column beside the maker's own number, and it is the bridge between how customers ask and how aftermarket stock is numbered. As of 3 November 2026, 66,479 of the 91,328 current lines in the lists we hold carry at least one, which is 73%. The other lines can still be found, but only by a request that names their own number.

Cross-references come from the maker's catalogue, which lists the carmaker numbers each of its parts replaces. Your stock system may already hold them in a field the export leaves out; it is worth looking. If you add them by hand, add only the ones you can trust. A wrong cross-reference is worse than none, because it puts your part in front of a customer whose car it does not fit, and the cost of that falls on the customer, on us and on you.

A genuine line needs no cross-reference: its part number already is the carmaker's number. An OE-brand line, made by a company that supplies the carmaker, has a maker's number of its own and matches a genuine number, and both should be in the list.

One part often replaces several carmaker numbers, so the genuine-number cell is allowed to hold more than one. Separate full numbers with a slash, a comma, a semicolon or a vertical bar, and each one is read. The table shows exactly how a cell is split, including the two cases that are quietly ignored.

The ignored cases exist to protect a match, not to punish a list. A fragment too short to be a carmaker's number on its own, and too long to be the trade's slash shorthand, cannot be read safely either way, so it is left out rather than turned into a number nobody wrote.

Part numbers are written in many ways: with dashes, spaces, dots, or none. Before two numbers are compared, everything that is not a letter or a digit is removed and the letters are made capitals, so the way your system writes a number never stops it matching.

The trade also writes families of numbers in shorthand. In 31410-12300/2, the short part after the slash replaces the end of the number, so the cell also means 31410-12302. Both numbers are read. A cell can also hold several full numbers when one part replaces several.

Matching forgives formatting and nothing else. It cannot tell that a letter O was meant to be a zero, that a digit was dropped, or that a suffix belongs on the end. Those differences are real differences between part numbers, and a reader that guessed at them would sometimes guess a different part.

The slash shorthand and lists of several numbers belong in the genuine-number column. The part-number column is read as one number: every separator is removed and what is left is the number. A part-number cell holding 31410-12300/2 is therefore read as 31410123002, and one holding two full numbers is read as a single long number that matches neither. A part-number cell with fewer than three letters and digits is set aside as unreadable.

If one box genuinely carries two of your maker's numbers, give it one row under the number printed most prominently, and put the other in the genuine-number column if it is a carmaker's number, or leave it out if it is not. If you hold two different parts that share a family of numbers, give each its own row.

Carmakers replace part numbers over time, when a part is improved or a supplier changes. The new number supersedes the old one, and catalogues move to it. Stock bought under the old number still has the old number on the box.

List the number printed on the box. If you know the newer number, add it in the genuine-number column beside it so either one finds the line. Never overwrite the box number with a newer one you are not sure of: a wrong number is worse than an old one, because it sends the wrong part to a customer.

Supersessions can chain: a number replaced once can be replaced again, so the same part may be known by three numbers across its life. Customers arrive with whichever one is on the part they took off the car. Each number of the chain you can vouch for, written into the genuine-number column, is one more request that finds your line. A supersession is not always a like-for-like swap, either: sometimes the newer part fits only with another change, which is why a guessed supersession does more harm than a missing one.

Many damaged part numbers were not typed wrong; a spreadsheet changed them. Spreadsheet software treats anything that looks like a number as a number, and part numbers often look like numbers. The fix in every case is the same: set the part-number column to Text before you paste or type into it, and check a few lines before you send the file.

Damage that has been saved cannot be undone from the damaged file. Once a CSV has been written with 986494524 where 0986494524 used to be, or with 1.23457E+11 instead of the full number, the missing characters are gone from that file. Go back to the source: export again from your stock system, or open the original CSV with the part-number column set to Text as it is imported rather than after.

Common spreadsheet programs keep only fifteen significant digits of anything they store as a number. A part number longer than that, stored as a number, loses its last digits for good and has them replaced by zeros. Formatting the column as Text first is the only protection.

When a list loads but its lines are rarely matched, the cause is often in the numbers. These are common signs, with what usually causes them.

A few minutes of checking catches most of the damage above, because spreadsheet damage is systematic: if one number lost its leading zero, every number that started with zero did. The steps below are in the order that finds problems fastest.

A genuine part, an OE-brand part and an aftermarket part can all be found through the same carmaker's number, so the number alone never says which one a line is. The brand column does. That is why brand is one of the four required columns, and why a list that carries the same number under two brands is two offers rather than a duplicate. What the grades are, and how they differ for a buyer, is set out in the guide to genuine, OEM and aftermarket parts in the UAE; how each grade is listed has its own page in this section.

A part number and a brand on a stock line are, between them, the description of the part, and UAE law takes a false description seriously, whoever the seller is. These are the rules as read on 4 November 2026.

If you sell online on your own account, the e-commerce law, Federal Decree-Law No. 14 of 2023, requires you to refrain from dealing in a misleading manner or giving incorrect data that does not truly describe the goods. Under the executive regulations of the consumer protection law, Cabinet Resolution No. 66 of 2023, which bind importers, distributors and sellers alike, a description is deceptive when it misleads about the producer, the country of origin, the country of export or the trademark.

The anti-commercial fraud law, Federal Decree-Law No. 42 of 2023, in force since 29 November 2023, makes it an offence to describe, advertise or display goods with false, deceptive or misleading data. It defines counterfeit goods as goods carrying, without permission, a trademark identical or similar to a registered one, and prohibits importing, selling or holding them for sale. The penalty is up to two years in prison and/or a fine of AED 5,000 to AED 1,000,000, and a seller is not excused because the buyer knew the goods were counterfeit.

For a stock list this comes down to the habits the rest of this page recommends: the brand column names the brand on the box, the part number is the one printed on the box, and a cross-reference goes in only when you can vouch for it.

This section is a summary of the law for orientation, not legal advice: the rules are in Federal Decree-Law No. 14 of 2023, Cabinet Resolution No. 66 of 2023 and Federal Decree-Law No. 42 of 2023, all on the UAE Legislation Portal, where the Arabic text prevails.