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Car parts explained: OEM vs Aftermarket

Car parts explained: OEM vs Aftermarket

When it comes to choosing spare parts for your car you're faced with the option of getting the part from the manufacturer, or from a third party supplier. We look at the pros and cons of each.

Most people choose to work on their cars, partly for the satisfaction it gives, but mainly because of the cost savings.

Garage labour rates can be extremely high, and so choosing to do the work yourself can work out considerably cheaper. But it's not just on labour where you can make savings – but also on the parts themselves.

What are OEM parts?

(Original Equipment Manufacturer) is the term used for parts supplied by a main dealer. While some of the components may be produced by the manufacturer themselves, many will actually be produced by preferred external parts suppliers, and are often rebranded by the manufacturer.

They are generally more expensive than comparable parts from third party suppliers, and are considered to be better quality – although in some instances there is negligible difference between the parts.


  • Guaranteed quality
  • You know it will fit
  • Potential buyers will prefer a car maintained with OEM components.


  • Extra cost
  • Possibility of having to wait longer
  • Some OEM parts are rebranded aftermarket parts, so are no different to third party. 

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Are third-party car parts reliable?

Due to the cost of some components, many enterprising companies produce their own alternatives. These are almost always cheaper than the OEM equivalents, and may also be more readily available, with plenty of online retailers offering collection or next day delivery – while main dealers may have a longer wait for parts, or not retail them via mail order.

Ultimately you have to weigh up the pros and cons. Say for example you need a new front wing for your car. It's likely that a third party wing will be considerably cheaper than an OEM one.

But it's also likely that it won't be made from as good quality material, and may need more work to make it fit. So it may not be the bargain it appears to be. Or consider an electrical component, a sensor for example.

There may be a cheaper equivalent made in the Far East at a fraction of the cost of the OEM sensor, but will it have gone through the same rigorous testing?

Will it be made to the same standard? Does the cost saving outweigh the potential for it not to last as long?

It's not unknown for cheap aftermarket suspension bushes to fail in the fraction of the time of the OEM bush – you pays your money, and you takes your chance! 

It's not unusual for a third party component to cost less than half of the OEM variant, and often it's unlikely it will last half the time, so in that instance (as long as swapping the component isn't too bothersome), it obviously makes financial sense.

There is a certain piece of mind that comes with buying OEM, plus, on occasion you may even find that the OEM part is the same price as the aftermarket offering, so it's always worth getting a quote.

Keep an eye out for main dealers who run online car parts websites, or use auction sites. These can on occasion throw up some genuine bargains particularly if it's a part for an older model, where the retailer wants to get rid of the old stock.

What about my warranty?

If your car is still under warranty, it's highly likely that fitting aftermarket parts will invalidate it – making it not worth your while opting for the cheaper option. It's always best to adhere to manufacturer guidelines, and fit genuine where practical.


  • Invariably cheaper, sometimes much cheaper
  • Good availability with quick delivery (usually)


  • Unknown quality
  • Potential to invalidate warranty
  • Increased risk of component failure