Genuine, OEM, matching quality, aftermarket: what the spare-part terms mean

The words genuine, OEM, matching quality and aftermarket do not grade a spare part’s quality by themselves. They say whose specification the part was made to, whose brand it carries and who vouches for it. Official texts define two classes: original parts and parts of matching quality. The European Commission’s guidelines also use OEM and OES; genuine and aftermarket are trade words.

How do official texts define an original part?

An original part is a wider class than the part in the vehicle manufacturer’s box. The Commission’s Supplementary Guidelines on motor vehicle agreements, issued in 2010 and amended in 2023, define it in paragraph 19:

“‘Original parts or equipment’ means parts or equipment which are manufactured according to the specifications and production standards provided by the motor vehicle manufacturer for the production of parts or equipment for the assembly of the motor vehicle in question”

European Commission, Supplementary Guidelines (2010/C 138/05), paragraph 19

Turkey’s Competition Authority applies the same test in Article 4 of Communiqué No 2017/3, which also counts parts made on the same production line. Its Guide lists three groups: parts the vehicle manufacturer makes; parts an independent manufacturer supplies to it; and parts that supplier makes to the same specifications and standards but sells directly to the market. Of the third it says: “These parts are also regarded as original spare parts.”

What do OEM and OES mean?

OEM and OES separate original parts by the brand they are sold under. Paragraph 18 of the guidelines names three sources: “parts bearing the trademark of the motor vehicle manufacturer (OEM parts)”; “original parts manufactured and distributed by original equipment suppliers (OES parts)”; and parts from matching quality manufacturers.

These abbreviations are not read the same way everywhere; the meanings here are the guidelines’. The Cambridge Business English Dictionary defines an OEM (original equipment manufacturer) as “a company that makes parts and products for other companies which sell them under their own name or use them in their own products”. So the guidelines’ OEM part carries the vehicle manufacturer’s brand; the dictionary’s OEM is the company that made it.

Genuine is no firmer. Australia’s competition regulator, the ACCC, wrote in a 2017 market study that original parts in the car manufacturer’s branding “are commonly referred to as ‘genuine’ parts”, and that submissions showed “no common agreement about the labelling of different kinds of parts”. When a quotation says OEM, ask whose brand is on the box and who made the part.

What is a part of matching quality?

A part of matching quality is not an original part, but has to stand comparison with one. Paragraph 20 of the guidelines: such parts “must be of a sufficiently high quality that their use does not endanger the reputation of the authorised network in question”. The vehicle manufacturer may bring evidence that a part falls short; the paragraph asks for no certificate.

The Turkish Communiqué does. Its spare part of equivalent quality (eş değer kalitede yedek parça) is one whose “conformity to criteria such as mass, dimensions, material and functionality”, found by comparison with the original, has been “certified by an accredited body”. Under the Guide that body must be accredited to ISO/IEC 17065 by the Turkish Accreditation Agency, or by an accreditation body party to a mutual recognition agreement under the International Accreditation Forum.

What do aftermarket, yan sanayi and muadil mean?

Aftermarket is the name of a market before it is a label for parts. Cambridge defines it as “the selling of new parts for cars that have already been manufactured”, and the recitals of Regulation (EU) No 461/2010 note that original equipment suppliers sell there too. As a label it is narrower: the ACCC describes aftermarket parts as “developed and made by an entity other than the OE manufacturer or car manufacturer”, generally meeting the car manufacturer’s specifications but possibly designed for different price points to differentiate on quality.

Yan sanayi and muadil are everyday Turkish words; neither appears in the Communiqué or the Guide. The Turkish Language Association’s dictionary defines yan sanayi as the auxiliary industry whose producers make products, parts and services “to the dimensions, forms and standards set by main-industry companies”, and the Guide notes that vehicle manufacturers have most of their parts made that way. Neither text says it outright, but together they mean that yan sanayi does not by itself mark a part as non-original.

Muadil is defined in the same dictionary by a cross-reference: eş değer, equivalent. The Communiqué’s equivalent-quality class exists only with a certificate, so if a part is offered as muadil, ask for it.

What do the rules say about independent parts manufacturers?

Both sets of rules protect the independent manufacturer’s route to market. The guidelines list among the Commission’s objectives “to protect access by spare parts manufacturers to the motor vehicle aftermarkets”; the availability of such parts, they say, “brings considerable benefits to consumers”.

Article 5 of the Regulation and Article 6 of the Communiqué remove the block exemption from an agreement in which a vehicle manufacturer restricts its parts supplier’s sales to independent distributors, repairers or end users. The Communiqué treats an agreement that stops an authorised repairer buying original or equivalent-quality parts elsewhere the same way.

One exception is written down: for warranty repairs, free servicing and recall work the vehicle supplier may require the original parts it supplies. If a part from another source causes a fault in paid work during the warranty period, the Guide gives no ruling: whether the warranty ends is to be settled “within the framework of general provisions”.

These definitions were written for road vehicles, commercial vehicles included; the Turkish Guide leaves motorcycles and tractors outside the Communiqué. The Regulation runs to 31 May 2028.

What should you check when you assess a part?

A part is identified by its maker, its paperwork and its dimensions, not by the label.

1. The manufacturer. Look for the brand on the part and the box. Regulation and Communiqué protect the supplier’s ability to mark its parts visibly, so that repairers and end users can identify the manufacturer.
2. The basis for original. Under the Guide, a supply contract with the vehicle manufacturer, plus the part manufacturer’s declaration that the parts it sells directly meet that contract’s specifications and production standards, creates a presumption that they are original.
3. The certificate behind equivalent. Who issued it, and is that body accredited to ISO/IEC 17065?
4. Dimensions and material. The Communiqué’s criteria are mass, dimensions, material and functionality. Compare the new part with the old one; the measurements worth taking on a pipe are listed in a separate article.
5. The record. The Guide lets a vehicle supplier require its authorised repairers to tell the customer beforehand when an equivalent-quality part is used, and to show the parts’ brands on the invoice. Ask for the same.

A counterfeit part belongs to none of these classes: the ACCC describes such parts as “parts of unknown origin which appear to bear the branding” of the car manufacturer or of a parts supplier.