Bosch vs NGK vs Denso Spark Plugs: Which to Choose | ToolingFun (2024)

Spark plugs…name an aftermarket part that has led to as much discussion as these fellas. Not only in terms of what brand’s the 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 go kaput. But which ones should you get? Let’s compare these spark plugs and find out. That should help you make an informed decision.

Choosing the Right Plugs for Your Vehicle

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. So, are NGK spark plugs good? Definitely. But is that a rule of thumb for all vehicle applications? No.

There’s only one rule I recommend you follow: stay as close to your OEM plugs as possible. Pick the same brand. That’s it. Your car maker used 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. For example, most of the Subaru or Honda models I’ve seen use NGK.
• As far as Bosch spark plugs go, you can expect them to appear in many BMW, Mercedes-Benz, and Volkswagen models. German maker, German cars.
• Attention GMC/Chevy owners: If your ride is a Silverado, Tahoe, or Yukon, I recommend these ACDelco plugs. ACDelco has always been the OEM replacement for GM vehicles.

Now, here’s a quick review of my impressions before I discuss the different spark plug materials.

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.

But why did I mention Denso’s remarkable power? One of Denso’s manufacturing 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 will make the ignition system go bust. So, are Denso spark plugs good? Absolutely, but you need to be careful. This 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.

Iridium, Platinum or Copper Plugs – What to Choose?

Before anything else, let’s get one thing straight. Most, if not all, of the spark plugs you see have the same core – it’s made of copper. When we’re talking about differences in materials, we’re referring to what the tip is made of. So, which is the best? Let’s discuss.

Iridium Spark Plugs

Manufacturers do try to push for the newest tech iridium spark plugs because they’re more expensive. Marketing, right? The truth, however, is that iridium plugs are actually the best choice if you’re looking for convenience. While they have the highest price tag, they’re also the most long-lasting spark plugs you can get – you can even hit some 80 000 miles with them.

Copper Plugs

If you’re looking for better conductivity and 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.

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

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

Platinum Spark Plugs

Moving on to platinum spark plugs – they’re right in the middle. Their longevity is less than iridium spark 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.

Mind the Plug Gap – 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 possible. Usually, your vehicle’s manual will mention the desired plug gap according to your car’s make. And usually, Bosch, NGK and Denso plugs will come factory pre-gapped.

But what if you need to do some gapping yourself? Well, the first thing is to get a reliable gapping tool. But it goes further than that – not all plugs can be gapped the same way.

So, one of the other benefits of copper spark plugs is that they’re the easiest to gap. Platinum and iridium plugs, on the other hand, 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.

If you’re curious about the whole gapping thing, there’s a Revzilla guide which I find pretty informative. So check it out – it might help you, too.

Ready to Make Your Choice?

There you have it – an overview of Bosch vs Denso vs NGK spark plugs. This post should help you make an informed decision next time you’re buying plugs for your car. Do your research and keep in mind that there’s no one-size-fits-all here. The spark plug selection simply depends on the type of vehicle you have and what you’re looking for.

Also, I want to point out that I talked quite a bit about Denso and Bosch in this post. But spark plugs aren’t the only arena of these two brands battling it out. If you’re searching for an oxygen sensor, be sure to check out my Bosch vs Denso sensors post and get the right sensor for your vehicle.

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