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The difference between genuine, OEM and aftermarket parts

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Updated 10 Oct 2019

Michael Jacobson

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If there’s one basic truth you can rely on in motoring, it’s that reliability is essential.

How you drive, where you drive, the age of your vehicle and the time between services all have an impact on reliability, especially regarding automotive parts.

General wear and tear or, in the worst-case scenario, damage from an accident, means you’ll probably need to buy replacement parts at some time during the life of your vehicle.

While used parts are always an option – although shop wisely – this article will focus on new replacement parts, weighing up the various types, features and benefits to consider before making your decision and shelling out the readies.

The genuine article

Replacement parts come in three categories – genuine, Original Equipment Manufacturer (OEM) and aftermarket.

First up, a genuine part is the one that was on your vehicle when it was manufactured and as it rolled off the production line.

Therefore, a genuine replacement part will carry the manufacturer's label, come in the manufacturer's packaging and more often than not cost more because of its genuine status.

As much as car purists or owners of new cars may prefer genuine parts, today many manufacturers are moving away from such bespoke production.

Instead, external companies are increasingly being contracted to make parts under the manufacturer's design and technical specifications.

The OEM option

Original Equipment Manufacturer parts are made by companies that initially did the job for the vehicle manufacturer.

In the case of OEM replacement parts, these won't carry the manufacturer's branding and they generally come in unprepossessing brown cardboard packaging – however, don't assume this is a reflection of compromised quality.

Furthermore, because OEM parts are produced for specific makes and models, you know they are going to fit your specific make and model.

That's a comforting thought, and here's another one – OEM parts are generally cheaper than genuine parts.

Happily ever aftermarket

Here's your best money-saving option, although there are a number of points to consider.

Aftermarket parts are made by companies other than the vehicle manufacturer and, as a result, may look different to genuine or OEM parts.

However, though able to be produced more cheaply and in greater numbers, this does not mean aftermarket parts offer less quality and reliability.

In some cases, they may be the better replacement option, especially if the maker has identified an opportunity to improve aspects of the original, thereby producing a part that is more durable, reliable and doesn't break the bank.

The counter to this may be some differences in performance, such as extra noise or vibration linked to a greater focus on grunt over purring.

More than the sum of its parts

As we said at the beginning, reliability is essential to motoring.

Whether you choose genuine, OEM or aftermarket replacement parts, each has its own particular virtues and subtle differences for you to ponder.

Finally, be sure to check your insurance policy before making any decision, because your cover may not go along with your choice.

And remember, our AutoGuru network is much more than the sum of its parts, with heaps of advice on all things motoring, and access to 1600+ qualified workshops or fully certified mobile mechanics.

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Written By

Michael Jacobson

Michael Jacobson is an award-winning Queensland-based writer.

His appreciation for motoring began as a young journalist covering racing from Simmons Plains in Tasmania.

Over the years he has interviewed many Australian and international motoring greats.

He has also been driven around Lakeside Raceway at ferocious speed, circumnavigated the Gold Coast Indy circuit at more than 200kmh and managed to squeeze 365,000 kilometres out of a Toyota Starlet.