Are OEM Spark Plugs Better Than Aftermarket?

When it’s time to replace your spark plugs, there are two kinds of spark plugs to choose from:

  1. OEM spark plugs
  2. Aftermarket spark plugs

If you’re here, you may have a few questions, such as:

  • What’s the difference between OEM and aftermarket spark plugs?
  • Which type offers more value?
  • Are aftermarket spark plugs even safe to use?

We'll answer these questions by covering the pros and cons of OEM and aftermarket spark plugs.

The Only Pro Of Using Aftermarket Spark Plugs

OEM spark plugs

There’s only one advantage aftermarket spark plugs have over OEM spark plugs, and it is…

Cost

There’s a reason the aftermarket market is booming. It’s because many aftermarket parts are much cheaper than their OEM counterparts. You can score a set of aftermarket spark plugs at a very low price.

Yet, there's something important to keep in mind: you get what you pay for. It may be OK to use certain aftermarket parts, like wheels. But you should avoid aftermarket spark plugs at all costs. Spark plugs are very important for the engine's performance, so it would be unwise to use a cheap set. To find out why, jump ahead to the section titled, "The Cons Of Using Aftermarket Spark Plugs".

The Pros Of Using OEM Spark Plugs

Spark plug specs

Check out the most common pros of using OEM spark plugs:

1. OEM Spark Plugs Come With The Right Dimensions And Exact Tolerances

Spark plugs are small parts that look simple. But the way spark plugs are designed is very important. Spark plugs need to come with the right dimensions and exact tolerances because:

  • Spark plugs help seal the combustion chamber. This prevents the fuel mixture from escaping. This also helps maintain combustion pressure.
  • Spark plugs need to provide a good connection point to either the coil or the spark plug wire.
  • Spark plugs need to have the right gap size to spark the engine on a consistent basis. If the gap is the wrong size, you'll experience some issues like poor fuel economy and engine performance issues.
    • Some engines need spark plugs with wider gaps. Others need spark plugs with smaller gaps.

OEM manufacturers design their spark plugs with the right dimensions and tolerances. For example, this OEM spark plug is only for certain 2013-2019 F-150, F-250, and F-350 trucks. It's to ensure longevity and reliable engine performance. OEM spark plugs are exact replicas of the stock spark plugs in your engine. So you won't have to worry about any fitment or tolerance issues.

2. Auto Manufacturers Build Their OEM Spark Plugs With High Quality Materials

The spark plug has many different components. Each component has an important role. All the components need to work together for the spark plug to function right. Auto manufacturers know this. That's why they build their spark plugs with high quality materials. This accomplishes consistent performance over a long period of time. Here are some of the quality components you can expect to find in OEM spark plugs:

  • Iridium-platinum alloy on the plug tip: This protects the plug from wear. It's resistant to the millions of explosions that occur within the combustion chamber.
  • Nickel coating on the plug threads: This makes the spark plug easy to remove after it has run its course.
  • Carefully crafted electrodes: This maximizes engine performance and fuel efficiency. OEM manufacturers spend a lot of time crafting the electrodes to very specific shapes. It's so they can pair the electrodes to the engine for which the spark plug is designed.

The high quality materials are part of the reason why OEM spark plugs can be expensive. Yet, not necessarily so -- jump to the last section of this post for more information.

3. Many OEM Spark Plugs Come With A Great Warranty

Many auto manufacturers warranty their OEM parts. That means if for some reason your OEM spark plugs don't work out, you can get them replaced for free. Look up your automaker's warranty policy for parts. Here are a couple of examples:

The Cons Of Using Aftermarket Spark Plugs

Let's explore some of the cons that come with aftermarket spark plugs:

1. Aftermarket Spark Plugs Don't Always Come With The Right Dimensions

Aftermarket manufacturers don't always follow OE specs when designing their spark plugs. This results in spark plugs that don't have the right dimensions and/or tolerances. That can spell disaster for the engine. It's because poorly designed spark plugs:

  • Don't always fire at the right time
  • Don't always provide the right amount of spark to maximize the engine's performance
  • Don't always seal the combustion chamber
  • May break within the combustion chamber (if not tightened correctly)
  • May wear out faster
  • May cause misfiring
  • May cause your vehicle to fail emissions due to the aforementioned issues

Amazon has lots of negative reviews about poorly designed aftermarket spark plugs. We rounded up a few:

  • "These aftermarket spark plugs were put into my Camry. They immediately started to misfire. I inspected them and found that one was not gapped correctly."
  • "My aftermarket spark plugs are a full 1/2" shorter than the OEM spark plugs. They started misfiring from the point I put them in. Also, the ends are weirdly tapered/scraped off by some machine. I had to put the OEM spark plugs back in."

2. Not All Aftermarket Manufacturers Build Their Spark Plugs With Quality Materials

p>Have you ever wondered why aftermarket spark plugs are so cheap? It's partially because many aftermarket manufacturers cut corners by using cheap materials. This leads to early failure and/or performance issues. Here are a few common issues caused by aftermarket spark plugs:

  • Aftermarket spark plugs can break within the combustion chamber due to being built with low grade materials. Some don't even come with nickel coating on the plug threads. Sometimes you may need to drill a broken spark plug out of the cylinder head, and that's a difficult job. Sometimes when a spark plug breaks within the chamber, metal pieces can fall down into the engine and cause significant engine damage.
  • Aftermarket spark plugs may cause electrical interference. Every spark plug comes with a resistor embedded in the ceramic housing. The resistor suppresses the RFI in the wire. When the resistor fails, the noise frequency can interfere with the vehicle's electrical system. Some aftermarket spark plugs come with weak resistors. Some even come without any resistors.
  • Cheap aftermarket spark plugs rarely come with electrodes that are the right shape or size. Using a spark plug with a cheap blade design will cost you engine power and fuel economy.
  • Cheap aftermarket spark plugs tend to fail early. Sometimes they'll even fail days after installation.

3. Aftermarket Manufacturers Rarely Warranty Their Parts

Many aftermarket manufacturers don't even warranty their parts. That's one of the reasons they can keep their prices down. So if you have a set of aftermarket spark plugs that failed, you'll have no choice but to:

  • Cover the repair costs (which can be quite high if the spark plugs caused engine damage)
  • Buy a new set of spark plugs

The Only Con Of Using OEM Spark Plugs

Spark plug cost

OEM spark plugs come with only one con, and it is...

Cost

There's a reason the aftermarket market is successful. It's because OEM parts can be quite expensive. Here's a secret, though: you can buy OEM parts online at wholesale prices! We're authorized sellers of OEM parts, and we offer rock-bottom prices for our parts. If you order your spark plugs from us, you get the best of both worlds:

  • High quality OEM parts
  • Wholesale prices that can be lower than aftermarket prices

Check out our extensive catalog of spark plugs for all makes and models. Chances are you'll find deeply discounted OEM spark plugs for your vehicle. Here are a couple of our best sellers:

If you need help finding the right spark plugs for your vehicle, we're here to help.