Are OEM Spark Plugs Better Than Aftermarket Spark Plugs?

The cost of spark plugs can add up, so it’s not surprising when some Mazda owners turn to aftermarket options. However, you might be wondering if it’s really a good idea to install aftermarket spark plugs in your Mazda.

If you ask us, our answer is no. You may save a few bucks on aftermarket spark plugs upfront, but they’ll likely end up costing you even more money in the long haul. Aftermarket spark plugs don’t always fit right, nor do they always function well.

While you can install aftermarket spark plugs in your Mazda, should you? To help you reach an educated decision, let’s take a look at the two most important factors in a spark plug:

1. Size

When it comes to spark plugs, size is really important. There is very little space between the electrode of the spark plug and the top of the piston, so the length of the spark plug has to be just right. The gap between the spark plug electrodes also has to be just the right distance.

If you install aftermarket spark plugs that aren't the correct size, you'll notice reduced engine performance and fuel economy. You may also run into some engine damage. Let's talk about some consequences of using incorrectly sized aftermarket spark plugs:

  • If the electrode gap size isn't correct, the spark plug can't optimally ignite the air/fuel mixture within the combustion chamber. More specifically, a gap that's too small won't leave much room for the flame to grow to the correct size. A gap that's too big might not even create a spark because the spark might not be able to jump across the large gap.
  • If the spark plug is too long, it'll extend too far into the combustion chamber and get hit by the piston. This can cause serious damage to the piston.
  • If the spark plug is too short, the air/fuel mixture does not get thoroughly burned. As a result, fuel is wasted and engine performance is reduced.

OEM Mazda spark plugs are designed with the right dimensions that allow the engine to run in the most efficient way possible. You can't really say the same about aftermarket spark plugs. Aftermarket manufacturers rarely design their parts to OEM specs. Even if you find spark plugs that are designed to OEM specs, chances are the dimensions are still off.

2. Materials

Since spark plugs are continually exposed to the high temperatures and other high-stress conditions inside the combustion chambers, they have to be incredibly durable. Even the most durable spark plugs in the world can't last forever in such tough conditions.

A good set of spark plugs can last from 50,000 to 100,000 miles. OEM Mazda spark plugs can easily last that long because they're built with durable, high-quality materials that can constantly withstand the heat and stress within the combustion chambers.

Aftermarket spark plugs are often inexpensive because they're built with inferior quality materials that can't really last in extremely hot and stressful conditions. Spark plugs play an important role in your engine's performance, so you want to get a set you can rely on for a long time.

OEM Spark Plugs Can be Affordable Too

The biggest reason car owners buy aftermarket spark plugs is because OEM spark plugs can be quite expensive. It's common for Mazda dealerships to mark up their prices by about 30% for OEM parts.

Here's a little secret: OEM Mazda spark plugs can be quite affordable if you skip the dealership and order them online. Actually, you would be hard pressed to find better prices than ours. At, we carry genuine OEM Mazda parts, including spark plugs, at very competitive prices. Take a look at our catalog of spark plugs to see how much money you can save on a set!