Platinum v.s. Iridium

Greetings all! I’m looking for opinions once more.

Practically since they came out I’ve been running Bosch’s Platinum Plus plugs in all the cars I change plugs on, including my own of course. NOT THE MULTI ELECTRODE plugs, the SINGLE electrode plug. I’ve been very happy with these plugs.

But now I’ve got to change plugs again and I’m considering a different brand of plug. NGK makes a plug called Iridium IX. They look more appealing than the Platinum plugs. I know that Iridium is a stronger metal but I’m not so sure if it’s better at conducting and whether the plug will produce a better spark.

Which plug is the better? The Bosch Platinum Plus single electrode or the NGK Iridium IX?

I know that sparkers are sparkers and brand and metal will not make a great difference. But when you’re paying three dollars and a quarter for a gallon of unleaded plus, even a small increase in mileage is worth what it takes.

So anyone with an opinion, a testimony, some specs or test results, a drunken rant maybe? Please, toss it in!


Thank you, Big Riveria. Now I know I’m not the only person crazy enough to worry about things like this. I’m probably not going to be very helpful. I suggest you buy whichever plug is less expensive. They are both high quality spark plugs, and I seriously doubt that either will make a measurable difference.

There are SO MANY things that influence fuel mileage. Spark plugs are just one minor component. Pick a plug, install them, and drive with fuel economy in mind. You’ll get the best mileage you can get.

By the way, I’m using Bosch Platinum plugs (single electrode) in my cars. My daughter, however, uses whatever is the least expensive, and her car ('05 Hyundai Accent) is getting FANTASTIC mileage. I have to wonder; is a spark plug a spark plug?

I have tested the primary circuit wiring connected to a honda distributor a few years ago by using a timing light. When I replaced the wires, I got fewer misses. I wonder if connecting the timing light pickup to the coil wire would show anything. If you got steadier flashing with one particular plug or another, that would be something to believe in. If you don’t notice any difference, we will never know you did a test unless you admit it. If there is a difference I would be happy to find out. Call it the double bogus testing method.

I’m surprised to hear all the comments about great perfromance using Bosch Platinum plugs. In our repair shop, we find them causing far more problems with misfires then they solve. In fact when we find them in a car with misfiring problems we usually recommend changing them.
I always advise customers to replace with the factory recommended plug. Motorcraft in Fords, AC in GM Products, Champion in Chrysler, NGK in most Japan built cars. You get the idea. I never install platinum or Iridium plugs in a car unless it origianlly came with them. Car manufactures spend huge amounts of money to squeeze every bit of fuel economy out of their cars. I don’t generally question that. Platinum and Iridium are used mainly to extend service intervals for spark plugs not to improve perfromance. This why plugs last 100k in newer cars. The only problem that comes up is actually getting the plugs out of the head after they have been in there for 100k. Sometimes they tend to sieze up in there.

All the designer spark plugs are 97.54% hype. Modern cars have good ignition systems and don’t need any help from special plugs. The plugs they came with are fine. About the only thing that might do better are platinum or alike plugs if they were not OEM and all that will buy you is more miles between changes.

If you like them, fine, they are not likely to harm anything other than your wallet. :-)

I can only describe it as a deceleration miss.
It usually happens when the car has been driven a while. Almost always in the summer months. Doesn’t happen all the time.
Car starts fine - has power. I’ll be cruising along on the highway, then if I very slightly lift off the gas pedal I get either one or a few misses. They appear to be a miss or a little shudder. Then it goes away.

What could this be?

2000 Hyundai Accent 45k miles.
Manual 5 speed of which I use 4
No A/C

Thanks in advance

I also suggest sticking with the OEM plug is the best choice in most cases.

I switched to the Bosch dual electrode plugs and have never ever been happier with spark plugs. What an amazing difference. They are platinum, though, so I don’t know about Iridium. I read a report once that said Iridium NKGs were okay but weren’t the best bang for the buck. Bosch dual electrodes are not expensive, either, if you get them at the Walmart, which is where I used to buy my ACDelco plugs until Walmart stopped carrying them. Glad they did 'cause that’s what made me check out the Bosch duals. LOVE 'EM. And so does my Alero.

Your fuel mileage is not going to be any better with platinum or iridium plugs in comparison to an inexpensive copper core, single electrode plug.

The only advantage to platinum and iridium, theoretically, is that they may last a bit longer.
They are not going to produce a hotter spark or anything else; the plug gap will determine that.
Some years back car makers used to recommend 15k mile plug changes. The Feds started mandating that plugs be a warrantable item (24k miles) OR, until the first recommended plug change. Platinum/iridium plugs pretty much guarantee the car maker won’t be paying for plugs under warranty.

The platinum/iridium plug will probably hold up better in those 30k miles (on average) than a regular copper core plug.
It’s been my experience that any plug will start misfiring to some extent anywhere from the 30 to the 50k miles mark. However, some of that misfire may not even be noticeable to the vehicle owner, but it’s there.

One area I never agree with is leaving plugs in for 75k, 100k, or whatever.

Agreed. It’s all “up-selling, up-grading” and shelf space. If these Bosch platinum plugs were so great, you would not be changing them and looking for something better.

In an 9.5 compression ratio unleaded fuel engine with electronic ignition, ANY spark plug will last a long time and never mis-fire. A spark is a spark. “You might want to try these, they have a “hotter” spark”. Countermen have been saying that for 100 years. It was BS then and it’s BS now…

Irridium is some 8 times harder than platinum so it erodes more slowly and conducts well for a longer period of time. But you apparently maintain your car well anyway, so it’s not really a big deal IMHO.

I’m an NGK fan. I’ve had misfires in the past with other brands.

The only advantage to platinum and iridium, theoretically, is that they may last a bit longer.

They do last longer…But I wouldn’t leave them in my vehicles as long as they claim. I like to change my plugs out once a year.

I have used the Iridium plugs but only because they were the only ones available for my truck. When I replaced them one year and 45k miles later…they looked great.

And as everyone has said…there is no performance increase what-so-ever with these plugs. They just last longer.

old thread, having extensive experience with Bosch +4 plugs, I was compelled to reply. The Bosch +4 plug will yield slightly better fuel mileage, and power, over a single tip plug. I’ve put them in cars with 100,000 miles on the clock, and run it another 100,000 miles and never had a problem. taking the plugs out to inspext them, all they had was light grey/white ash deposits from the crappy gasoline we used to get. this was on a Saturn DOHC twin cam, 16 valve engine w/stick shift 5 speed, and another Saturn DOHC twin cam with automatic trans. it’s the other way around actually, iridium is “supposed” to last longer, that’s all there is to it. if they made a 4-tip or even 2-tip iridium plug, I’d buy it. logic being, all the old military fighter and bomber planes of the pre-jet, pre-1950 era, used MULTI TIP PLUGS- for a reason, when you’re at 15,000 feet you can’t afford to have a cylinder go down in the engine. if one tip gets fouled, the spark simply goes to the next tip closest. simple logic and it works. single tip plugs burn the gap open, no matter how good they are, and then the engine goes rich due to the spark having to jump a wider gap. then the O2 sensor reads it, and leans the hell out of the engine, and will also start throwing bank1, sensor 2 codes for the O2 sensor voltage and heater circuit. all because the damned plugs burned open, but the engine is still running. albeit too lean. so get the +4 plugs and you’ll be far ahead.

+4’s are also easy to install, no gapping required, and the way the gap is configured, makes the tip self-cleaning, the spark jumps across the tip to get to the electrode, keeping the tip clean. there is no electrode to burn down, it’s flush with the ceramic. I believe it’s call a “surface gap”.

I’ve since run the plugs in two different GM 3800 series II V6 pushrod engines, and the same noticeable improvements. typically fuel mileage will go up 1-2 mpg and a tad more power. as I type this, I’m putting the +4 Bosch plugs in a 2005 Dakota w/3.7 liter V6 SOHC engine. the local auto stores don’t stock them anymore, but you can get them online, but they’re well worth the wait. as a sidenote, I could have bought the single tip iridium Bosch plugs, for $2 CHEAPER per plug on Ebay, but am waiting for the +4 plugs instead. I’ve been a mechanic and engine builder since 1981- need I say more ??? just do it, get the +4 plugs- IF you can find them anymore.

if you run standard copper plugs, be prepared to change plugs every year or two. a real PITA anymore on new cars. the only reason the industry got away from multi-tip, is they are expensive to manufacture, a single tip is cheaper, but substituting a single iridium tip, they can get longevity near or equal, or slightly longer than the platinum +4, but not the same mileage, power, or reliability factor as a multi-tip plug. all the air forces of the world didn’t run them because they were into gimmicks, they ran multi tips because it was mandatory for performance and reliability during wartime.

  1. Please point out an actual controlled study that backs your claim of increased MPG.
  2. Please send a birthday card to this thread in May when it turns ELEVEN YEARS OLD.

Gary_Williams post is SPAM. Please remove this drivel.


If you are only changing them out once a year so they don’t seize in the spark plug holes, but they are still “like new”, you could just screw them right back in. Rotate the plugs like tires once a year.

@cdaquila Carolyn, it seems that Gary Williams revived a 10 year old thread just to post Spam.


Perhaps I am just a bit Dens-o, but I read it a couple of times and I didn’t think it was spam. If it was spam, it was awfully thoughtful and didn’t even link to a way to buy what he was pushing. No sarcasm intended, but can’t he just really like Bosch +4 plugs?

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Maybe spam isn’t the right term. Guerilla marketing or conflict of interest might be more appropriate.

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