NGK vs Denso: Which Is The Better Spark Plug?

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There’s a lot of talk about NGK vs Denso and which is better between the two spark plug makers. But we have to be honest here.

You see, there is no definite answer. All the rumors about NGK vs Denso are probably just the result of plain old gossip from rumormongers. The best type of spark plug for any type of vehicle can be found in the one thing that most car owners neglect: the owner’s manual.

Modern engines are manufactured using extreme tolerances. Any degree of deviation from a faulty or wrong part will significantly affect the engine in a variety of ways. I’m not just talking about the spark plug here. Changing or modifying basic engine components such as the air intakes and the spark plug wires might not always result in squeezing out the best possible performance.

Sadly, it’s the same with spark plugs. And it doesn’t even matter if the spark plugs are NGK or Denso.

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Comparing NGK And Denso Spark Plugs

It won’t be similar to comparing apples and oranges. But it’s more like discerning the difference between a Fuji and Red Delicious apple. Both are types of apples, but they don’t taste the same, and both have a different texture.

But in order to arrive at a definite conclusion, it is best to compare NGK and Denso plugs in the same category. For purposes of fairness and equality, I will compare iridium spark plugs from Denso and NGK. 


The NGK Spark Plug Co. (short for Nihon Tokushu Togyo Kabushiki-gaisha) was established in 1936. The main headquarters of NGK is located in Nagoya, Japan. Is there any wonder why the best car parts are made in Japan? Denso is also from Japan, but NGK is a universal brand of spark plug and is renowned all over the world.

The NGK Iridium IX is a spark plug designed to offer lasting ignitability, superior anti-fouling characteristics, and sharper throttle response. This can all be attributed to the iridium alloy tip that ensures consistent performance even in extreme hot or cold weather.

What makes the NGK Iridium IX stand out is the longer insulator nose. This feature is engineered to prevent fouling even after 100,000 miles. The Iridium IX also comes with corrugated ribs on the insulator. This feature prevents spark flashover to maintain proper combustion whether sitting in traffic or going full speed on the racetrack.

My personal experience with NGK Iridium IX is nothing but bliss. After bolting them inside the motor, simply set and forget. The only time you’ll need to replace them is after 70,000 or 80,000 miles, which is less than the claimed 100,000-mile durability of Denso iridium plugs. But the mileage will vary depending on the type of vehicle and daily operating conditions.

Whatever the case, the main reason for purchasing iridium spark plugs is longer service life, which will help reduce overall maintenance costs. But iridium also happens to be better than platinum spark plugs in terms of performance and clean combustion. As an added plus, iridium spark plugs help the motor to consume less fuel.

But the most compelling reason why NGK has an edge over Denso is availability. It is easier to source NGK spark plugs (for any type of vehicle) at online shops and retail stores compared to Denso.

And if you have a Japanese car, the vehicle will most likely be equipped with NGK spark plugs. 


In order to steal some of the spotlight from NGK, Denso needed to come up with a different type of iridium spark plug. They managed to come up with the Iridium TT. The ‘TT’ part is the twin tip technology.

What this means is the Denso Iridium TT is equipped with two tips: a 0.7-millimeter Platinum ground electrode, and a 0.4-millimeter iridium center electrode. This design delivers less obstruction between the ground and electrode to offer an omni-directional spark, which is a fancy way of saying it produces a larger explosion inside the combustion chamber.

Improved combustion is always a good thing. This means the engine performs better and sips less fuel. In fact, Denso claims the Iridium TT produces the largest spark concentration and explosion among iridium spark plugs. That’s a bold claim, but does your engine actually need an omni-directional spark to maintain smooth and reliable performance?

Again, the answer will depend on the type of vehicle. If the manufacturer recommends Denso Iridium TT plugs, it means the motor is calibrated for the Iridium TT. Installing a different type of iridium spark plug may not produce noticeable losses in performance, but it may affect engine tolerances upon extended use. This might lead to accelerated wear and tear to vital engine components.

As if all that technology is not enough, Denso went the extra mile with the Iridium IX. The spark plug is precision-welded using Denso’s exclusive 360-degree laser welding technology to ensure lasting performance. Of course, all of this comes at a price since iridium spark plugs costs as much as 3x more than platinum spark plugs. 


NGK vs Denso: Which Is The Better Buy?

If price is your main concern, the NGK Iridium IX is cheaper than the Denso Iridium TT, although not by much. If you swap the stock iridium NGK plugs with Denso spark plugs, you might notice no difference in engine performance, especially if the manufacturer recommends both brands.

But we’re only talking about untouched, bone stock vehicles. If you have a modified or tuned motor, the only way to find out which between NGK and Denso is better is by trying it for yourself. The compatibility of the spark plug will depend on the type of motor and the level of tune.

But for the money, I personally like NGK, but only because all the cars I owned were fitted with NGK plugs in the first place.

More reading on spark plugs in the V6 engine.

George Bradley
 

George is an enthusiastic blogger and an auto mechanic expert whose mission is to provide the readers with the best tips, guides, and recent events in the automotive industry. He has been involved in researching on various topics that are essential to the car owners, especially when it comes to an understanding, maintaining and handling their vehicles.

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