Denso vs NGK – Which Spark Plugs Should You Use?


The day will inevitably come when you have to change your vehicle’s spark plugs and choose between two of the largest parts manufacturers in the world—Denso or NGK. Both companies make similar spark plugs but the slight variations between the two products leave many car owners wondering which product is superior. At the end of the day, though, the answer comes down to price.

On the surface, Denso and NGK’s iridium spark plugs offer the same high level of performance but, thanks to their thicker electrodes, NGK’s plugs usually last longer than their competitors. Over the lifespan of your vehicle, this can save you both time and money, leading us to conclude that NGK’s plugs are superior. 

In this guide, we’ll carefully review both products and discuss how they perform in different situations. We’ll compare their construction, endurance, and price so that, by the end, you should have all the information you need to make an informed decision about which spark plugs to buy.

What Type of Spark Plugs Do Denso and NGK Make?

Before purchasing a spark plug, it’s imperative to always check the type of product you’re buying. Spark plugs come in three different varieties—platinum, copper, and iridium—which perform better under different conditions. If you’re purchasing Denso or NGK products, be sure that you need iridium plugs rather than the other two varieties.

Iridium spark plugs, like those made by Denso and NGK, are designed for modern engines. They have a smaller tip that’s better able to withstand the heat and pressure of high-performance engines, allowing them to last far longer than other types of plugs. They are ideal for anyone wanting to avoid the hassle (and expense) of changing their plugs frequently and are standard across most Japanese car brands.

Comparing Construction and Materials

Now that we’ve discussed the types of plugs that Denso and NGK make, let’s compare their construction and materials. Both companies use iridium in their electrode tips, which is the hardest metal used in spark plugs today. This is ideal because it means that the tips will last longer and won’t need to be replaced as frequently.

Denso’s spark plugs are designed using a U-groove design, which offers better sparking performance, whereas NGK uses a V-groove, which is more resistant to carbon fouling. When it comes to the materials used in the construction of the plugs, both companies use similarly high-quality metals, making it harder to compare the two.

The main sticking point between their designs, though, is that NGK’s electrodes are significantly thicker than Denso’s. This means that NGK’s spark plugs can better withstand the heat and pressure of high-performance engines over a longer period than Denso’s plugs. While this might not affect performance, it does translate to greater endurance.

Comparing Overall Performance

In terms of performance, both Denso and NGK’s iridium spark plugs offer excellent results. They’re both designed to work well with modern, high-performance engines and, thanks to their iridium tips, they’re both resistant to wear and tear. The main difference between the two is that NGK’s plugs usually last longer than Denso’s, thanks to their thicker electrodes.

This increased endurance is especially important if you have a high-performance engine that puts greater stress on your spark plugs. In these cases, NGK’s plugs will usually last longer before they need to be replaced, saving you both time and money. Of course, if your vehicle’s engine doesn’t need as much endurance, NGK’s plugs may seem over-engineered.

Comparing Price Points

On a one-to-one basis, NGK’s spark plugs are roughly 38% cheaper than Denso’s, costing just $29.99 compared to $41.28 for a pack of Denso plugs. Considering that NGK’s plugs are also designed to last longer, they’re clearly the more affordable option. Yet, some car owners may prefer to use Denso plugs because they perform better.

Thanks to Denso’s unique U-groove design, their plugs offer better sparking performance than NGK’s. In terms of raw performance, then, Denso’s plugs are superior.

However, many car owners are willing to sacrifice a little performance for the increased endurance and lower price of NGK’s plugs.

The decision, then, comes down to price and performance. If you’re looking for the best bang for your buck, NGK’s plugs are the way to go. If you’re willing to pay a little extra for better performance, though, Denso’s plugs are the better option.

How Long Should a Spark Plug Last?

Iridium spark plugs can last for a long time. Most people report that they get about 30,000 miles (48,000 kilometers) out of a set of iridium spark plugs. However, it’s important to keep in mind that the lifespan of your spark plugs will vary depending on the make and model of your vehicle, your driving habits, and the quality of the spark plugs you purchase.

If you want your iridium spark plugs to last as long as possible, it’s important to follow the manufacturer’s recommendations for replacement intervals. In general, it’s a good idea to replace your spark plugs every 20,000 to 30,000 miles (32,000 to 48,000 kilometers), but you may find that some brands, such as NGK, last longer.

Related: Why Is There Oil On My Spark Plug Threads?

How to Tell if Your Iridium Spark Plugs Need to Be Replaced

Regardless of the brand, you’ll be able to tell if your spark plugs need to be replaced by looking for certain symptoms. If your vehicle is experiencing any of the following issues, it’s a good idea to check your spark plugs and, if necessary, replace them.

  • Trouble Starting the Engine: The most obvious sign that your spark plugs are failing is if your engine refuses to start. If it takes longer than usual to engage the engine, it’s a good idea to check your plugs.
  • Decreased Fuel Efficiency: Has your vehicle’s fuel efficiency decreased recently? If so, it might be time to replace your spark plugs. Over time, spark plugs can become fouled with carbon deposits, which can affect how well your engine runs. NGK plugs are designed to reduce carbon fouling but they too will eventually succumb to damage.
  • Loss of Power: If your vehicle seems to have lost power or is struggling to accelerate, it might be due to faulty spark plugs.
  • Increased Engine Noise: Spark plugs that are worn out or damaged can cause your engine to run louder than usual. If you notice an increase in engine noise, it’s a good idea to check your plugs.
  • Rough Idling: If your engine is idling roughly, it could be a sign that your spark plugs need to be replaced.
  • Check Engine Light: In some cases, your vehicle’s check engine light will come on if the spark plugs are failing. If this happens, it’s important to take your vehicle to a mechanic to have it diagnosed.

The Takeaway

Both Denso and NGK make high-quality iridium spark plugs but, thanks to their thicker electrodes, NGK’s plugs usually last longer than their competitors. Over the lifespan of your vehicle, this can save you both time and money, leading us to conclude that NGK’s plugs are superior. Nevertheless, both brands offer quality and performance so choose based on your vehicle’s needs.

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