Replacement Car Parts Guide: Genuine vs. OEM vs. Aftermarket

Cars are something that we rely on every day. Whether getting to work, shopping or busing the kids to school, we expect cars to work each and every time we turn the key or press the start button. But there will be times when your car won’t budge. Assessing the problem and locating replacement parts can become an ongoing task, costing you valuable time and money.

If your vehicle is still under warranty, the dealer can do the work for you. They’ll use parts from the manufacturer with appropriate warranties, often lasting between 12 and 24 months. For those that have older vehicles, buying replacement car parts opens up a world of possibilities.

Assessing What’s Wrong 

This is the initial hurdle before you start shopping. Warning lights in the dash can give you a rough idea of the issue. 

To find what component is at fault, you need to do a vehicle diagnostics test with the OBD port hooked up to a computer or scanner. The issue will be pinpointed and displayed as a set of codes, essentially a series of letters and numbers.  

Decoding OBD Codes 

Letters are displayed first, signalling either an issue with the body (B), the chassis (C), the powertrain, or engine and transmission (P) or as a communication fault (U). What follows is a series of numbers. 

The first number after the letter is 0 or 1, with 0 meaning a generic code and 1 a manufacturer-specific code. The following number pinpoints where the problem is. 1 is the fueling and air metering, 2 is the fuel injection circuitry, 3 is the ignition, 4 is the exhaust or emissions systems, 5 is idling or cruise control, 6 is the ECU and 7 and 8 is the transmission. 

The last two digits define the specific issue at hand. For instance, an OBD code P0302 signals a generic powertrain issue with ignition failure in the second cylinder. You’ll need to check the spark plug or plugs, the ignition coil, or the plug wires.  

Shopping for Replacement Parts 

You can go the brick-and-mortar route or shop online once you’ve figured out the problem or talked with your local mechanic. 

Online stores have the upper hand here. They often have a wider selection of different brands. And they simplify shopping by providing quick ways to find car components specifically for your vehicle by entering your make, model, and production year. The parts will be clearly specified as OEM, OEM-replacements or aftermarket.  

Prices are also lower than those offered by traditional brick-and-mortar shops which have rent and employee costs that find their way into the final cost. Online stores also simplify ordering, offer different payment options, and have same-day deliveries. You can have your order delivered to your doorstep or specified address which is convenient if you don’t have a vehicle to get the parts yourself.  

Shopping for auto spare parts is the simple process of having your Vehicle Identification Number (VIN), something you can find on the driver’s side of the windscreen or the side door or door jamb. If you can get to the faulty components, these also have a part number or code. 

Retailers and online sellers also list vehicles compatible with a specific part. It may not be the same brand as the existing part, but an aftermarket replacement that works just like the original.  

Genuine, OEM-replacement, or Aftermarket? What to Choose?

Genuine models are those made by the vehicle manufacturer. These are vehicle or make-specific. But there are also dozens of generic models used by different car brands. 

For spark plugs, you may have a hard time finding a car maker that also produces their own genuine spark plugs. In this case, you can go with OEM (Original Equipment Manufacturer) brands that are quality tested across the range of vehicles the car maker produces to ensure that they work as they should. 

Toyota, for instance, uses Denso spark plugs across the board and will push buyers into buying from the same brand. This is because buyers believe they’ll get guaranteed quality and the products will perform as new and last for the specified warranty or be replaced free of charge if they fail beforehand. 

However, going with aftermarket options shouldn’t be seen as a negative. In most cases, aftermarket replacement car parts exceed strict carmaker requirements and perform even better than OEM or genuine alternatives. A whole industry is devoted to bringing the best out of your car, precisely with better-engineered aftermarket options.  

What differs here is pricing. While price differences are rare for genuine or OEM tailored to work with your car, you have more variation in the aftermarket. You can find cheaper replacements for OEM components or more expensive options that add more performance or last longer. The only downside here is that aftermarket products can void your car warranty.  

Choosing Online Stores 

The benefits of online retailers are obvious. But with so many online dealers, buyers need to make a well-researched decision as to where to shop. 

As a general guide, look for stores that cater to different vehicle brands, with a wide selection of OEM, genuine and aftermarket options. Not everyone will want OEM car spare components, and many buyers are looking for aftermarket upgrades and willing to spend some more. Also, look for stores with detailed information about products, including part numbers and vehicle compatibility.  

Next is availability. You have no use in sticking with a particular part reseller if what you need is out of stock or needs to be ordered due to low demand. Well-stocked stores should have parts available at all times and be ready to deliver them when needed.  

Also, look for customer reviews. Customer service can make or break a company, and dissatisfied shoppers won’t hesitate to voice their views. Stores need to have qualified staff with a wide knowledge of the inventory they sell and be ready to offer sound advice to any queries. Look for stores that also feature on multiple platforms and have defined contact information.  

Lastly, regard a store’s warranty and return policies. Buyers can be delivered faulty products, and a well-defined return policy will save hassle and frustration. In addition, parts that fail prematurely should be changed out with a valid warranty.  


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