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Universal aftermarket injectors: Why 'one size' fits none (Part 1)

Although aftermarket parts companies often highlight the ‘universal fit’ of their products as a positive product attribute, this means that aftermarket parts will never fit your car’s exact make and model the way an OEM or remanufactured OEM part will.

Picture of filled car parking lot.

While the aftermarket part may not necessarily be poorly produced, even slight differences in fit can have an impact on the way these parts contribute to your vehicle’s performance and longevity – especially when it comes to fuel injectors.

If you are on the fence about purchasing universal injectors, read on to learn a bit more about them, and the associated risks with installing them in your vehicle.

What are aftermarket parts?

An aftermarket auto part is any replacement part for a vehicle made by a third party manufacturer. Although aftermarket parts are designed to function the same and are often the least expensive part replacement option, the quality and reliability of aftermarket parts varies greatly.

Most aftermarket parts are mass produced to fit a variety of vehicles, typically referred to and marketed as 'universal-fit' or 'universal' parts. Universal parts are designed and manufactured to fit several different makes and models, just like the name suggests.

However, while aftermarket companies often promote the universal-fit of their parts as a convenient, cost-saving benefit, these types of parts come with several challenges that should be considered when the time comes to replace your fuel injectors.

Due to the universal nature of aftermarket parts, the fit on your specific vehicle will be significantly variable – especially when it comes to injectors.

"But why is this so important?", you might wonder.

Answer: It has to do with tolerance.

Tolerance? What's that?

Parts are never made to perfect specifications. Due to unavoidable variations caused by material characteristics and manufacturing processes, parts will always be made larger or smaller than their nominal design. This variation is captured in design as tolerances, depicting the range of variation acceptable in the design.

Essentially, tolerancing is the process of determining acceptable upper and lower limits on part dimensions throughout the manufacturing process to account for the inevitable size variations in the manufacturing process.

But when it comes to fuel injectors, why does tolerance matter?

While there might be a time and place where universal parts will not impact the drivability or performance of your vehicle, for example, with floor mats or seat covers, this is certainly not the case with your fuel injection system.

Fuel injectors have a manufacturing tolerance of 1-2 microns, which is the finest tolerance of any mechanical component of the engine. This means extreme precision throughout the manufacturing process is imperative to the performance of fuel injectors.

All OEM or remanufactured OEM parts are designed and manufactured with extreme precision, meaning that they are manufactured with extremely low tolerances (i.e.1-2 microns) specific to the exact make and model of the vehicle in which they are being installed, which guarantees that each injector produced will be an exact fit for the vehicle it was made for.

Since aftermarket injectors are universally designed to fit several different types of vehicles, third party manufacturers typically produce injectors that require large tolerance ranges throughout the manufacturing process to accommodate for the many vehicles the one part must be compatible with.

In doing so, third party manufacturers produce injectors with significantly higher upper and low lower tolerance limits.

So, what does this mean for you and your vehicle?

Let's say you happen to go for the universal aftermarket injector.

If your vehicle happens to have dimensions that fall near the middle of the tolerance range used to manufacture the universal injector, it might happen to work just fine for your vehicle.

However, if your vehicle’s make and model tolerances fall closer to the upper or lower limits of the aftermarket manufacturer’s tolerances, you will likely deal with several issues with the fit of the aftermarket part in your vehicle, which causes a range of issues down the line, and likely, a trip back to the repair shop.

Installing an injector that is too small will:

  • Reduce power at wide open throttle

  • Cause engine damage from detonation

  • Reduce fuel injector life

Installing an injector that is too big will:

  • Reduce power at small throttle openings and create idle problems

  • Cause damage when excess fuel washes oil off the cylinder walls

  • Foul spark plugs

Here's the bottom line: When it comes to fuel injectors, 'one size' fits none.

Although the initial price-tag of universal aftermarket injectors might be appealing to consider for your vehicle at first glance, these types of injectors can cause a breadth of issues that may lead to a higher cost for you, and your vehicle, down the road.

Of all the reasons you should consider remanufactured OEM fuel injectors, fit is among one of the most important considerations. When GB’s remanufactured OEM fuel injectors are installed, you are guaranteed the OEM form, fit, and function for your vehicle’s specific make and model.


Curious to learn more? Visit our Knowledge Center, packed with fuel injection-related articles and topics to assist you in better understanding fuel injection systems and technologies.


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