Are OEM Spark Plugs Worth It?

A spark plug isn’t a part designed to last forever. Come time for replacement, be it your first service or fifth, you have two options:

1. Grab whatever the local auto parts store is pushing that week on sale

2. Buy a genuine set of OEM replacement plugs

Which do you need - the OEM quality plugs or a cheap set of aftermarket plugs? Although we obviously promote the use of OEM, it’s not just because of our bias. Check out the rundown on the differences between your two options and you’ll see why we always recommend OEM plugs in your Mazda’s engine.

OEM Is Superior In Structure

OEM Maz Spark Plug

It’s hard to see the OEM difference with your eyes because the difference is in the materials and specifications. When you buy an OEM Mazda plugs, this is what you get:

Top Quality Ceramic Insulator: Low-quality insulators are more likely to fracture during installation, or later when the temperature rises. However, since most people can't tell the difference between one ceramic to the next, low-cost spark plugs often use poor-quality ceramic material to save money.

Nickel-Plated Spark Plug Shell: The purpose of the metal casing around the plug shell is to protect the plug and secure the spark plug in your engine’s cylinder head. OEM quality plugs have a nickel-plated steel shell since nickel prevents corrosion and is far less likely to seize in the heads than other materials. Most aftermarket plugs have a super-thin coating of nickel or none at all.

Electrodes Made of Platinum or Iridium: OEM Mazda spark plugs have a platinum tip with a lifetime rating of 90k miles or an iridium tip with a lifetime rating of 120k miles. These are both costly metals, so aftermarket brands often use low-grade platinum or iridium to cut their costs. They don't last as long as OEM plugs as a result, but most of the after-market brands are banking on the fact that you'll forget about their poor quality when their "iridium" tipped plugs fail after 60k miles instead of 120k. (More about failing spark plugs here.)

High-Quality Interference Suppression Resistor: Spark plugs send out a lot of electromagnetic signals when they fire, and these signals will interfere with your Mazda’s electrical components. To keep this from happening, an interference suppression resistor in each plug prevents noise interference with your vehicle’s electronics. Cheap interference resistors produce static in your speakers, interfere with the function of your navigational system, and can even impact important sensors like those for your ABS, crank position sensor, and other key parts. The average aftermarket plug brand uses substandard interference suppression resistors and takes a gamble with your vehicle’s ability to resist the signals from the plugs.

Precision in Fitment and Design on the Body and Electrodes: Engine tolerances are extremely tight so your spark plug needs to be an exact length. Even a measly few hundredths of an inch too long and the electrodes can cause valve or piston interference. A little bit too short and combustion will be incomplete. Aftermarket plugs tend to be on the lower side so they can save on the manufacturing process without the risk of a longer plug - i.e., they know you probably won’t notice that it’s their plug causing lower engine efficiency so they play it safe while saving themselves money. OEM plugs are all uniform in length, electrode size, shape, and gap for precise efficiency.

Why OEM Plugs Matter To You

So you’re just looking to throw a set in your car and you’re not worried about the next service interval, you just want to save money now, right? Well, you’re not accomplishing this with aftermarket plugs. Those cheap plugs are going to start costing you at the gas pump right away.

To break it down, if your aftermarket plugs have low-grade tips, an incorrect gap, lack of precision in the electrode profiles, or are too short, your fuel economy is going down. The decrease isn’t going to be huge unless there’s something way off about the plugs, but it adds up. If your Mazda gets 24 mpg and you drive it 15,000 miles a year, paying $3 a gallon for gasoline, a mere 2% loss of economy will cost you $37.50 in the first year.

If those cheap plugs last for a few years, you can end up flushing $100-$200 down the drain in fuel. Compare that to the set of quality plugs you buy from us and you haven’t saved a dime - not to mention you’re going to need to replace those cheap plugs much sooner.

In Conclusion

OEM plugs were made to promote the best performance from your Mazda. Aftermarket plugs are a little cheaper, but that’s because important corners have been cut when it comes to materials and manufacturing. Maximize performance and efficiency by using OEM plugs. If nothing else, you’ll save hundreds at the pump!

Want more help choosing the right OEM spark plugs. Check out the spark plugs buyer's guide.