What's your take on Iridium spark plugs?

[Farmer Dan]

Auto parts guy tried to talk me into the NGK 6637 plug and explained all the advantages of the new iridium plugs.  I don't think any of them will by seen by the Eldo motor so I stuck with the normal NGK 7333.  What do you guys think?  anyone try them?

[atavar]

I have a pair in the main side of my Norge and they have given me no problems.  Here's what they look like after running two seasons.  I didn't replace them.

[kevdog3019]

Put them in my V11 Lemans and noticed a good difference.  Tried them in my older Lario and no difference.  I feel they foul easier so if I were using carbs I wouldn't go there, FI try them you may feel a better pull and quicker response.  My buddy noticed it in both his V11's also.  Supposedly a bigger kernel.  Worth the experiment I feel from my (our) experience.

[ibis1]

Run them in my Jeep Grand Cherokee and love them. They are also NGK, which I think makes as good a plug as anyone. Some vehicles will run on anything, but some show a BIG difference from 1 plug to another. Heat range has a lot to do with it, so it's always good to pull a plug after a few thousand miles to inspect it for the correct heat range for your driving. Good luck.

[Hymes Inc.]

Have only tried them on fuel injection. Giving E3's a shot on my V65C.

[kirkemon]

I've had the Denso iridium in my W650 for a long time - seems like they last about 3 times what a normal plug would - but they're 3 times the price!

[canuguzzi]

Hawk running with carbs, they work great. Norge has them too, no issues.

[Chuck in Indiana]

Snake oil, kinda.. <shrug> Yeah, they last longer, but what's the point when standard plugs are dirt cheap? Now, if it's a $50 airplane plug and you need 8 of em for your four cylinder engine.. that's a different matter.

[Wayne Orwig]

Iridium plugs are mainly just designed to last longer. They only real advantage is that the smaller electrodes can generate a spark more easily than a fat electrode, so they are less likely to foul.

If you see an improvement, then your butt dyno is probably broken, or the old plugs were simply bad.

[Farmer Dan]

Thanks for the input guys.  Sounds like the only advantage is that the local shop has these in stock.  Guess I'll save me a 20 mile trip and give them a try.

[ibis1]

Iridium plugs are mainly just designed to last longer. They only real advantage is that the smaller electrodes can generate a spark more easily than a fat electrode, so they are less likely to foul.

If you see an improvement, then your butt dyno is probably broken, or the old plugs were simply bad.

OMG, I've got to disagree with the "Improvement" statement. My Jeep definitely idled better than it was new with the original plugs. I'm not saying everyone will benefit. Some people may notice a negative effect. There are way too many variables to make a statement that you will notice an improvement. Some will and some won't. There is no way of telling until you try. Also, most plug manufacturers produce these plugs and some will work better in certain applications than others, another variable. You will never know until you try.

[Dofin]

I ran NGK standard plugs in my PC800, carburated, got average 47 mpg for 10s of thousands of miles.  Switched to NGK iridium and after more than 3K miles I am getting an average of 53 mpg.  I tow a trailer with my 2 stroke bikes on it, average mileage was 35mpg with standard NGK after switch last month towed to Deals Gap with an average of 38 mpg!!  No butt dyno here it got better mileage after the change!

Did a oil and plug change to iridium on my V7 havent had a chance to do a good milage check.  I did do a short trip for camping on the V7 with standard NGK plugs, with my camping gear, 600 mile round trip and mostly 70 mph or less I got pretty much the same as the PC 47-50 mpg.

[toaster404]

No rational explanation.  VL800 cruiser did much better - still new looking plugs at 30,000 miles.  Mileage improved.  Previous plugs were normal NGK and looked fine.  Ford 4 cylinder Ranger pickup.  Replaced with 8 Iridium many years ago.  Pain in rear to get to 4 of those.  I pull one every once and a while.  Might just be showing wear, and I have no idea when they went in!!!  Truck always starts perfectly and runs perfectly, although the check engine light comes on randomly.  1991 Ranger with 240,000 miles.

So I just use them whenever I replace plugs.  Seem to work better.  Can't see why!

[kevdog3019]

It's kind of like saying all gas is created equally and it's snake oil to run premium or ethanol free. It's still gas right? It takes gas and a spark. Change one of those factors and sometimes you will notice something. Iridium a have a more intense (dramatic) spark. Some will, some won't, so what... but if you've never tried it, well...

Why do they dual plug heads?

[Kev m]

Aren't today's electronic ignition systems operating with higher voltage coils than something from 70's?

Not to mention they generally have more active timing control.

These might be factors that help prevent fouling and allow for longer life or perceived differences when used in some (seemingly more modern) applications.

[kevdog3019]

Aren't today's electronic ignition systems operating with higher voltage coils than something from 70's?

Not to mention they generally have more active timing control.

These might be factors that help prevent fouling and allow for longer life or perceived differences when used in some (seemingly more modern) applications.

So you're saying they've changed voltage to increase efficiency?  So why use plugs from the 70's?  Look... I'm only playing devils advocate to show that (perhaps) plugs with a better spark can make a difference.

[sib]

Indium plugs are OEM on my Prius, and they fit in perfectly with my attitude about cars:  I want to have to think about my car's maintenance as little as possible, and have someone else do any required maintenance.  The plugs last 100,000+ miles and I'm not going to think about them at all.

I have a different attitude about my motorcycle.  I enjoy maintaining it, and I'm going to be pulling the plugs avery 6000 miles anyway, so I might as well replace them with new, freshly gapped, un-fouled ones.  Therefore, I'm not interested in indium plugs for the motorcycle.

Different beasts, different attitudes, different plugs.

[Rough Edge racing]

Aren't today's electronic ignition systems operating with higher voltage coils than something from 70's?

Not to mention they generally have more active timing control.

These might be factors that help prevent fouling and allow for longer life or perceived differences when used in some (seemingly more modern) applications.

 Not necessarily...The high voltage  ignitions of the later 70's-80's were needed to fire the large plug gaps. Large plug gaps, .060, were needed to fire the lean mixtures used then before modern engine management systems.Remember the 8-9 MM fat plug wires ? ..Now with more sophisticated  engine controls using coil on plug, the fuel air mixtures are held to 14.7 during normal engine loads and this doesn't generally require wide spark gaps or 50K volts...Of course many newer engines have high compression ratios that might require higher voltage to fire the plugs at wide open throttle..As a side note, the 14.7 air fuel mixture is a result of three way catalytic convertors needing this ratio to function properly..And this ,and higher HP, is the reason many new vehicles get worse fuel mileage than 90's vehicles...
  In the 60's 4 inch bore V8's and bikes with 11-1 compression could rev to 7000 or more RPM with points ignition.This all worked ok with the rich fuel mixtures used back then...
 

[timonbik]

Just put iridiums in the  auxiliary 4 stroke outboard on my sailboat.  Had the easiest/fastest post winter start up ever in 15 years of ownership.  Just sayin.....

[BRIO]

On the inner plugs of the Norge they make sense because of the extended interval and work involved.

[Kev m]

No, that's not what I meant, let me try this again from a computer instead of a phone.

I'm under the impression that MODERN (i.e. current ignition systems) are capable of producing higher voltages that earlier systems (solid state or not).

If this is true I was guessing that it was part of the equation why modern motors can benefit from long-life, precious metal spark plugs vs. traditional copper core plugs that wear away (increasing the gap).

But maybe I'm wrong, maybe it's mostly on the air/fuel ratio (better engine management to prevent fouling) and timing strategy (more active engine timing management to match ignition to ideal conditions) that allows these plugs to be of a benefit.

Bottom line my point was that chances are much greater that a 1970's motor will foul precious metal plugs (cancelling any benefit to their use) long before a modern motor. As such, it might make more sense to just use the standard copper core plugs and replace them more often.

[Rough Edge racing]

 Kev, I got a bit carried off topic....According to NGK for example, precious metal electrode plugs fire at lower voltages and last longer than conventional plugs...
   Many well respected engine tuners claim a higher voltage ignition will NOT improve performance if a "lower" voltage ignition was doing it's job...Many of these same tuners dislike thin electrode precious metal plugs claiming they invite detonation more so that a more conventional plug...
   I use NGK G precious metal race plugs with a slightly wider gap in my vintage Triumph racer because it idles better ........A lot of times new or different spark plugs make the engine feel a bit more responsive or better fuel mileage. I believe the new plugs are masking another problem, like a marginal ignition or fuel delivery issue..

[canuguzzi]

Spark plugs in a properly tuned and maintained engine used as designed shouldn't be fouling in the first place.

This thing about high voltage ignition; once you get past what is actually needed it is no more than the same marketing used to sell all the liquids that claim to improve engine performance.

There is a difference between more and better but more seems to sell. More cubes, more HP, higher voltage, higher octane, just an extra couple psi , etc.

When it comes to MG though, it isn't like they use the best practices when it comes to sending stuff out the door so if Iridium plugs gives seat of the pants better results, why not?

[Kev m]

Norge P - I wouldn't assume a 1970 anything was currently "properly tuned and maintained" - and I'll go further, I wouldn't assume that even if it was that it would offer the same conditions in the combustion chamber to take advantage of whatever the precious metal plugs seem to offer (which is mostly longevity). But yeah, if it works and you don't mind the cost over standard, go for it. Of course, standard might work just as well for less.

Kev, I got a bit carried off topic....According to NGK for example, precious metal electrode plugs fire at lower voltages and last longer than conventional plugs...
   Many well respected engine tuners claim a higher voltage ignition will NOT improve performance if a "lower" voltage ignition was doing it's job...Many of these same tuners dislike thin electrode precious metal plugs claiming they invite detonation more so that a more conventional plug...
   I use NGK G precious metal race plugs with a slightly wider gap in my vintage Triumph racer because it idles better ........A lot of times new or different spark plugs make the engine feel a bit more responsive or better fuel mileage. I believe the new plugs are masking another problem, like a marginal ignition or fuel delivery issue..

I hear ya, and I'm not saying that higher voltage improves performance, but certainly higher voltage will make up for problems (like a widening gap or potential fouling), no?

I would assume the precious metal plugs don't generally require higher voltage, unless they start to become fouled. Would the resistance added to the circuit then draw a higher voltage to fire them in that circumstance?

But yeah, I guess it's more the fuel management and timing area of modern motors that allow people to take advantage of the precious metal plugs.

Again, my conclusion would be it's probably a waste in a 1970s ________________.

[oldbike54]

 Wait , now I'm confused . Isn't the copper used in regular spark plugs a better conductor than iridium or platinum ? How would a less conductive metal allow for higher voltages ?

 Dusty

[Toecutter]

I can tell you that putting a resistor plug in a resistor cap will create a whole pile of problems!

Ehh. I tried iridium plugs in my CB750, wasn't worth the cost.

[kevdog3019]

We can't solve the worlds problems nor can we ever agree on plugs. Try them... if your bike runs better, you might want to use them. Maybe it's masking other issues or deficiencies, but aren't there deficiencies anyhow. I mean you could say a heavy flywheel or rods are a deficiency. They are cheaper to test than either of those. Don't try them if you think their snake oil, but don't tell others that if you've never tried them. I've learned to try stuff first and keep an open mind. I've also learned more people are closed-minded than the contrary.
Ha!

[Kev m]

Wait , now I'm confused . Isn't the copper used in regular spark plugs a better conductor than iridium or platinum ? How would a less conductive metal allow for higher voltages ?

 Dusty

Don't know the answer to the first, but I don't believe anyone said the second.

That said, if resistance increases voltage in the circuit (I still stumble on electrical theory) then widening gap would increase resistance, which in turn increases voltage (V = I x R)?

[oldbike54]

Don't know the answer to the first, but I don't believe anyone said the second.

That said, if resistance increases voltage in the circuit (I still stumble on electrical theory) then widening gap would increase resistance, which in turn increases voltage (V = I x R)?

 So in other words ... I really think some of the thinking here is backwards , in the real world shouldn't a copper conductor outperform a less conductive metal . Yeah , the gap thing and all , but what am I missing here ? Seems basic physics still applies .

 Dusty

[kevdog3019]

So in other words ... I really think some of the thinking here is backwards , in the real world shouldn't a copper conductor outperform a less conductive metal . Yeah , the gap thing and all , but what am I missing here ? Seems basic physics still applies .

 Dusty

A person that knows just enough can sometimes be dangerously naive.