Bosch vs NGK vs Denso Spark Plugs: Review and Comparison

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Spark plugs…name an aftermarket part that has led to as much discussion as these fellas. Not only in terms of what brand’s best, but also regarding the best type to put in your car.

Let’s talk about Bosch vs NGK vs Denso spark plugs. These three are the usual suspects if your OE parts went kaput.

I’ve always felt a bit uncomfortable when people go crazy about a particular brand. Personally, I think NGK’s latest IX spark plugs are the best choice…

But is that a rule of thumb for all vehicle applications? No, there’s only one rule I recommend you to follow:

Stay as close to your OEM plugs as possible. Pick the same brand.

That’s it. Your car maker put a certain manufacturer and type – that’s what works the best with your vehicle’s anatomy. Don’t steer away from that.

Most Japanese cars run on NGK or good quality Denso. Most of the Subaru or Honda models I’ve seen, for example, use NGK.

As far as Bosch spark plugs go, you can expect them to appear in a lot of BMW, Mercedes-Benz and Volkswagen models. German maker, german cars.

Attention GMC/Chevy owners: If your ride is a Silverado, Tahoe, Yukon, you name it…I recommend you these ACDelco plugs. ACDelco has always been the OEM replacement for GM vehicles.



Now, a quick review of my impressions before I discuss the different spark plug materials:

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NGK Iridium IX

NGK Iridium IX



  • Best iridium spark plugs out there.

  • NGK is the OE choice for most Japanese vehicles.

  • King of durability – easily the longest lasting spark plug right now.

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Denso TT Platinum

Denso TT Platinum



  • TT = Twin Tip tech for faster acceleration.

  • Price for performance is the best with platinum plugs.

  • Pretty durable and well-manufactured.

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Bosch Double Iridium

Bosch Double Iridium



  • OE on a lot of BMW and Mercedes models.

  • Copes well with heat and stays durable overall.

  • Not as fancy as NGK plugs, but costs a little less.

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Now, if your car manual lets you choose between two brands, that’s another story.

In that case, I’d recommend grabbing a set of NGK spark plugs. There’s a reason why this brand dominates OEMs.

NGK plugs are well manufactured and have the lowest failure rate from what I’ve seen around. The spark potential is not as powerful as Denso, but NGKs will last you way more miles than any other brand.

Inline Bosch vs NGK vs Denso

But why did I mention Denso’s remarkable power?

One of Denso’s manufacture benefits is the TT system. ‘Twin tip’ technology, as they dubbed it. The double tip achieves a larger explosion within the combustion chamber. Technically, Denso has the best power…as long as your vehicle can support that.

On some models, this is going to make the ignition system go bust. Which takes us back to the stick to your OEM specifications mantra. If you’re curious, here’s how the TT works:

Let’s talk about spark plug materials now.

Bosch vs NGK vs Denso Spark Plugs:
Should you choose iridium, platinum or copper?

Before anything else, let’s get one thing straight. Most, if not all the spark plugs you see have the same core – it’s made of copper.

When we’re talking about difference in materials, we’re referring to what the tip is made of.

So which is the best?

Well, manufacturers do try to push for the newest tech iridium spark plugs because they’re more expensive. Marketing, right?

The truth, however, is that if you’re looking for convenience, iridium plugs are actually the best choice. While they have the highest price tag, they also last the longest – you can even hit some 80 000 miles with them.

If you’re looking for better conductivity and better performance, you should stick to copper spark plugs. Copper steamrolls over iridium and platinum in these areas, but it suffers from a significant drawback:

Copper spark plugs die out way faster than the other two types. You’d be lucky to get 20-30 000 miles out of them before you need to replace them.

Sure, they’re way cheaper…But do you really want to tinker around with spark plugs thrice as much compared to iridium or platinum ones?

If you want quality copper, check NGK’s V-Power (prices here). Alternatively, you also have Denso’s traditional copper plugs.

By the way, here’s a good guide on how to ‘read’ what’s up with your plugs:

You’ll see copper as the OEM preference for a lot of older vehicles, like the 80s or even some very early 90s ones.

Speaking of platinum spark plugs – they’re right in the middle. Their longevity is less than iridium plugs, but more than copper ones. With most makers you can expect some 50-60 000 miles out of them.

Why? Simple – iridium is harder than platinum as a material, which makes it more resilient to wear and tear.

Platinum spark plugs have two kings. One is NGK’s G-Power I’ve recommended for some Toyotas.

The other – Denso’s legendary TT plugs. These two are easily the best platinum plugs on the market in terms of performance, manufacture, and reliability.

Spark G Power NGK

NGK G-Power

Best platinum spark plugs out there. Durable, good performance, A+ style NGK design.

Best platinum spark plugs out there. Durable, good performance, A+ style NGK design.


Gapping: it matters

Every spark plug has its gap – the distance between its two electrodes, center and ground. If you want everything to run smoothly, you need to adjust it as accurately as you can.

Usually, your vehicle’s manual will mention the desired gap according to your car make. And usually, Bosch, NGK or Denso plugs will come factory pre-gapped.

But what if you need to do some gapping yourself?

The first thing is to get a reliable gapping tool. But it goes further than that.

So, one of the other benefits of copper spark plugs is that they’re the easiest to gap.

However, platinum and iridium plugs are trickier. Some say they can’t be gapped – they can, but you need to be extra careful. The reason? Both iridium and platinum center electrodes are fickle and brittle easily.

If you’re not careful, you might just scrape off the coating, affecting the longevity of your spark plugs. The tool I linked above is a bit better than the usual coin-style spark plug gappers in this sense. It’s still risky, though.

Gap Tool for Spark Plugs

If you’re curious about the whole gapping thing, there’s this Revzilla guide which I find pretty informative.

Also, here I talked quite a bit about Denso and Bosch. Spark plugs aren’t the only arena of these two brands battling it out. If you’re in search of an oxygen sensor, check out my Bosch vs Denso sensors post.

Last but not least, as always – let me know of your own spark plug adventures. What did you end up using, and are you satisfied with your choice?