What Does Interchange Part Number Mean? A Guide for the Aftermarket Industry
Author: Jon Hedges
Jon has 40 years of marketing experience in the automotive aftermarket industry.
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What is an automotive interchange part number?
An interchange part number is way to show that an aftermarket or remanufactured part number is compatible with the original OEM factory part.
Automotive part number interchanges are powerful cross-reference systems. They identify automotive part numbers from different manufacturers that are interchangeable with the original factory part. These are primarily replacement automotive parts for maintenance or service repair.
(And of course, the term “part number” has become generic and includes all alpha-numeric part identifiers, with both letters and numerals.)
The part manufacturer in this case can be several things. It can be the original equipment manufacturer (OEM) like Ford or General Motors. It can also be a tier 1 supplier (manufacturers that supply parts to OEMs) selling parts into the aftermarket, like Denso or Bosch. Or, it can be manufacturers that took on the role to design, produce and sell their own version of replacement parts.
Interchange part numbers, also known as crossover part numbers, also play a role in the used automotive parts or remanufactured parts markets. Remanufactured automotive parts are called “reman” for short. Reman automotive parts rely on interchanges to identify compatibility, because they can’t be marketed as the same, original OEM part number. Used parts are the original OEM parts.
Interchange automotive part numbers and parts
Parts interchanges and crossover part numbers are a way to let parts shoppers identify which automotive parts from different manufacturers are interchangeable with the original factory part, by using it as a cross-reference guide for finding compatible replacement parts. Part number searches are used on Google. These search patterns indicate high purchase intent, and are what is called “bottom of funnel” or “BoFu” searches.
It is fairly common for a tier 1 manufacturer to supply a part to the OEM, to be packaged under the OEM brand, as well as sell the exact same part under their brand. This massive translation system ties everything together, showing that parts with different numbers are actually the same part, or represent the same part.
Why do automotive parts have different part numbers?
Many people wonder why the same exact part can have different part numbers. There are several reasons this happens in the automotive world.
In the case of OEM replacement part numbers, it all starts with the OEM. They’re responsible for millions of parts so the part numbers they assign are quite long. Over time, these OEM parts get changed slightly or the sourcing changes, so the part number has to change as well.
Aftermarket products never intended to be direct replacements for OEM parts don’t have the same problems as OEM parts and their counterparts.
Disappearing hyphens and part number supersessions
Many OEM part numbers include hyphens. These hyphens often get dropped as these part numbers propagate around the internet.
In the alternator image above, an example is the Ford part number GR3Z10346Q. This Ford part number was originally “GR3Z-10346-Q.” As part numbers get added to databases, extracted for websites, get copied and pasted, the hyphens often disappear. That’s why you’ll see “GR3Z-10346-Q” and “GR3Z10346Q” as the same thing. You may even see spaces instead of hyphens, like “GR3Z 10346 Q”.
Here’s another reason another alternator part number showed up. At some point, something about that alternator changed. It was superseded with part number GR3Z-10346-J inside Ford Motor Company. That, in turn, got edited or evolved somewhere down to GR3Z10346J without hyphens, which is how it appears on some websites.
By the way, Google has gotten really good at understanding part numbers with missing hyphens.
OEM part numbers in the aftermarket industry
That alternator is sold through Ford dealers as GR3Z-10346-J. But, Ford sells that alternator as a Motorcraft® brand with the part number GL8966. In fact, if you open the Motorcraft box the alternator probably has another Ford part number, in this case GR3T-10300-AC (or similar, there are several variations). Technically, since the Motorcraft alternator is available for purchase outside an automobile dealer it is an “aftermarket” part.
But who really made that alternator? Ford didn’t. Our bet is Denso, a tier 1 electrical component supplier to Ford. Denso can’t sell the alternator to the aftermarket as an OEM Ford part or a Motorcraft part, so it sells it to the aftermarket as Denso part number 104210-6900. That, of course, can also turn into 1042106900 without the hyphen.
Part numbers with multiple fitment
Adding to complexity is vehicle fitment. Officially, Ford alternator GR3Z-10346-Q is a 175-amp alternator that fits the 2015-2023 Mustang with a 2.3L EcoBoost engine and heated driver’s seat. You can find the crossover part number GR3Z-10346-K online, but it’s a 200-amp alternator that is supposed to also fit Mustangs with the 3.7L EcoBoost that came with a 200-amp alternator, or the 5.0L Mustang that came with a 175-amp alternator.
Are OEM parts better than aftermarket parts?
OEM parts aren’t necessarily better than aftermarket parts. In fact, many times aftermarket replacement parts are manufactured and distributed by an OEM’s tier 1 supplier, and are the same as the original OEM part. In the case of the alternator above, the same part can have an OEM part number, an OEM’s “aftermarket” brand and part number, or a OEM’s tier 1 brand and part number. In some cases the tier 1 manufacturer sells that same part as a private label part to another distributor or reseller, and is marketed as a different brand altogether.
Hollander Interchange System: The grandaddy of interchanges
The problem of crossover and interchange part numbers started showing up in the early 20th century. During the Great Depression in the 1930s, Roy and Hildur Hollander started to compile a list of crossover part numbers.
That became what is today the The Hollander Interchange®, now owned by Solera, an automotive software company in Texas.
The Hollander Interchange includes nearly 2 million (!) part fitment applications. It is claimed to cover 95% of all the vehicles in North America.
Today of course it’s all digital and online. Long-time industry veterans may remember the time when the Hollander manuals were printed on dead trees. This photo of a well-worn Hollander interchange manual is from the late 1980s and this thing weighed a lot!
It wasn’t uncommon to see these in automotive parts businesses and automotive repair shops, all marked up with notes and paperclips. When 3M came out with Post-It® Notes in 1980 it was considered a minor miracle in the automotive aftermarket!
How part number interchanges interchange
At it’s most basic level, an interchange system speeds up searching for equivalent parts, as it cross-references part numbers, vehicle models, and vehicle manufacturers. This dramatically reduces the time spent looking for replacements, allowing mechanics and suppliers to quickly locate the correct part.
Two-way vs one-way interchangeability
Not all interchange relationships are the same. There are two main types:
Two-Way Interchangeability: This means Part A can replace Part B, and Part B can also replace Part A. Most parts in an interchange group work this way.
One-Way Interchangeability: This means Part A can replace Part B, but Part B cannot replace Part A. This usually happens when a newer, improved part can replace an older one, but the older part shouldn’t be used to replace the newer version.
Interchange part numbers and automotive SEO
Of course interchange or crossover part numbers have an important role in automotive SEO! These crossover part numbers improve your website’s visibility with search engines and with AI.
When shoppers search for automotive parts online, they don’t always use the same part numbers. They don’t always find the same part numbers on websites, either.
A single product might be searched for, using dozens of possible part numbers, depending on what information shoppers have.
Understanding consumer search patterns for automotive parts
Automotive enthusiasts and do-it-yourselfers (DIYers) search for parts and accessories using predictable search patterns. This creates a major SEO opportunity for automotive retailers who understand interchange relationships and want to improve their automotive SEO.
Interchange part numbers give you multiple entry points for the same product
Each interchange part number represents a potential search query that could lead customers to your website’s product page. For example, if you’re selling an alternator that has five different interchange part numbers, you have five different ways customers might search for that exact same product.
By optimizing your product page for all these numbers, you can capture much more search traffic. Well-designed product pages include appropriate crossover part numbers.
Keyword expansion strategy for part numbers
Smart automotive SEO practitioners use interchange data to expand their keyword strategy far beyond the primary part number. If your alternator originally fit a 2015 Ford F-150, but the interchange data shows it also fits 2008-2017 Ford Expeditions, your product page could include all those part numbers and vehicle fitments.
Capturing long-tail searches
Customers often search using very specific combinations like “2014 F-150 alternator CL-3T-10300-AA.” If a shopper is very technical or experienced, they may even search on the engine, like “CL3T10300AA 220 amp alternator 5.0L.”
If your product page includes all interchange part numbers in the content, meta descriptions, and product specifications, you can rank for these highly specific, low-competition searches that often have higher conversion rates. In the case of this F-150 220 amp alternator these crossover interchange part numbers could include 104210-6270, 104210-6660, AL3T-10300-CA, AL3Z-10346-C, and CL3Z-10346-A.
Wrapping up crossover interchange part numbers
Hopefully you learned a little about how interchange numbers work and how they play a role in optimizing automotive websites for SEO and AI. If you have more questions reach out to us.
Frequently asked questions
Q: What is an automotive interchange part number?
A: An interchange part number comes from an interchange cross-reference system that identifies which OEM, aftermarket or remanufactured parts are compatible replacements for the original OEM factory parts.
Q: Why do the same automotive parts have different part numbers?
A: There are several reasons why an automotive part can end up having different part numbers. OEMs assign long part numbers to millions of parts, and these numbers change when parts are modified or sourcing changes. Additionally, tier 1 suppliers often sell the exact same part they supply to OEMs under their own brand with a different part number. Aftermarket manufacturers also create their own numbering systems for replacement parts they can’t market as original OEM parts. Finally, if an original part number included hyphens, those are sometimes dropped as part numbers get propagated across the internet in different databases.
Q: What’s the difference between two-way and one-way interchangeability?
A: Two-way interchangeability means Part A can replace Part B and vice versa. Most interchange relationships work this way. One-way interchangeability means Part A can replace Part B, but Part B cannot replace Part A. This typically occurs when a newer, improved part can replace an older version, but the older part shouldn’t be used to replace the newer one.
Q: What is The Hollander Interchange system?
A: The Hollander Interchange® system is the automotive industry’s most comprehensive crossover part number system. It was started during the Great Depression in the 1930s by Roy and Hildur Hollander. Now owned by Solera, it includes nearly 2 million part fitment applications and claims to cover 95% of all vehicles in North America. It’s the industry standard for identifying compatible replacement parts.
Q: Why do part numbers sometimes appear with or without hyphens and spaces?
A: As OEM part numbers get copied into databases, websites, and various systems, formatting often changes. Hyphens frequently disappear, and spaces might replace hyphens. For example, Ford part number “GR3Z-10346-Q” might appear on a website as “GR3Z10346Q” or “GR3Z 10346 Q.” Search engines like Google have become sophisticated at recognizing these variations as the same part number.
Q: How do interchange part numbers help with automotive SEO and online sales?
A: Interchange part numbers create multiple entry points for customers searching for the same product online. Each crossover part number represents a potential search query, allowing automotive parts retailers and eCommerce businesses to capture more search traffic by optimizing product pages for all relevant part numbers. This strategy helps capture long-tail searches and highly specific queries that often have higher conversion rates, as customers using technical part numbers are typically further along in the buying process.
Q: Are OEM parts better than aftermarket parts?
A: OEM parts aren’t necessarily better than aftermarket parts. In many cases a part is manufactured by an OEM tier 1 supplier, and sold as an OEM part, sold under an OEM’s aftermarket brand, sold under the tier 1 supplier’s brand, or sold as a private label part under another brand.
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