OEM stands for original equipment manufacturer, and OEM parts are the components, both on and inside a vehicle, that came from the company that first produced them when the vehicle was new. 

In the past, auto manufacturers produced all the parts that went into their products, so they were the source of all OEM parts. But, because of the complexities of car design and intricacies of business it’s common for automakers to contract out production of some parts. In those cases, the source of OEM parts is not the car company. It’s the company that produced the part.

Once you know about OEM parts, it’s easy to understand aftermarket parts. Aftermarket parts are manufactured by companies that are not the original manufacturer. They’re the opposite of OEM parts. 

In many cases, aftermarket companies design their parts to fit a variety of makes and models. So, an automaker might manufacture an OEM windshield wiper blade for a specific make, model, and year. An aftermarket company, though, has a blade that works with that specific vehicle but also many other makes, models, and years. 

Aftermarket parts cost less money than OEM parts. Why is OEM more expensive? How can aftermarket part manufacturers sell for less? 

When an automaker develops a new part, they invest a lot into design and testing for durability and safety. Those costs are reflected in the pricing. But the aftermarket is a narrower investment. It only makes specific, reverse-engineered parts spread across a wider number of makes and models.  There’s less for the aftermarket to recoup and more scale toward individual parts. 

Aftermarket parts are not just cheaper. Sometimes, they’re better. In fact, there are times where the aftermarket is faster at addressing design flaws found in original parts. 

In an article for Utility Fleet Professional on aftermarket vs OEM parts, OG&E fleet manager Paul Jefferson, explains how “Aa few years back we had some pickups that had fuel gauge problems because of how the fuel sending unit was designed. I read an article about how the aftermarket had already identified [the problem] and so we switched.” 

In the same article, the fleet services supervisor for Virginia-based Fairfax Water, Dale Collins, CAFM, explains that although he uses OEM for critical components, he has solved specific problems with aftermarket solutions. “Oftentimes the aftermarket tends to do a better job at re-engineering a weak area in an OEM part,” says Collins said. “Years ago, we went through a lot of belt tensioners. The bearing itself wasn’t sufficient to support the load, so the aftermarket responded and put in a more robust bearing, which solved a lot of the problems.

Across asset-heavy industries, including manufacturing and fleet, managers and maintenance teams need reliable methods to decide between OEM and aftermarket parts. OEM stands for original equipment manufacturer, and are parts produced by the companies that first made them when the asset was new.

Aftermarket parts are basically the opposite: parts made by a third party, not the original manufacturer. Both come with their own sets of pros and cons. With OEM, you remove a lot of the unknowns in terms of fit, quality, and performance. However, OEM parts are more expensive and can sometimes be harder to find, especially for older equipment and vehicles. With aftermarket parts, the lower prices often come with drops in quality and life span.

That said, there are times when aftermarket parts incorporate fixes to known design flaws still present in OEM parts. When deciding between OEM and aftermarket parts, you should look at existing warranties and insurance, the criticality of the component, and the age of the equipment.

In many cases, your insurance dictates which type of part you can use. When it comes to critical parts, it makes sense to go with OEM because of the higher quality and better fit. But, with older vehicles, aftermarket might make more sense.

You don’t want to pay more for a new OEM part guaranteed to last five years only to install it in a car with only a few years of useful life left.