Spark Plugs

kcirdnek · Jun 23, 2005

I know that this forum is mostly about oil/grease/lubrication, but I had to ask this question somewhere.

Which spark plugs are best for cars? Iridium or Platinum?

If Platinum, which one:

BOSCH Platinum +4 4458

BOSCH-PLATINUM 4205

NGK G-POWER Platinum 3403

NGK LASER TYPE Platinum 7862

BOSCH-PLATINUM_2 4305

AUTOLITE_PLATINUM AP106

CHAMPION_DOUBLE_PLAT 7013

CHAMPION_DOUBLE_PLAT 7940

AC-DELCO O.E. PLATINUM 41-943

SPLITFIRE_3_PLATINUM TP10D

CHAMPION_DOUBLE_PLAT 3013

AUTOLITE_DOUBLE_PLAT APP106

If Iridium, which one:

DENSO IRIDIUM 5325

NGK Iridium 7164

Right now, I have the BOSCH Platinum +4 4458 in there. They have been in there for a little over a year and I have not had any problems from them. But, I am going to be doing a major tune up pretty soon, and I just wanted to see what was preferred.

y_p_w · Jun 23, 2005

I personally have my doubts about the Bosch aftermarket platinum spark plug design. You've probably seen it - a thin platinum wire buried flush at the end of the insulator. No "heat range" per se; I don't know how that tiny platinum wire is supposed to draw enough heat to the core to prevent it from melting. A Japanese car specialist I go to told me that they found an alarming number of them where the center electrode just vaporized away.

Since you've said that AC Delco platinum is O.E., I believe NGK makes many of the AC Delco platinum plugs, and probably the ones you're looking at. What car?

I like the NGK ("Laser") or Denso double platinums. A correct iridium plug from either would be OK. The NGK G-Power platinum only has a single platinum spot on the center electrode, and the limit of longevity will be the erosion of the ground electrode. I'd go with a standard (V-Power) plug over the G-Power.

Jon · Jun 23, 2005

The answer: it depends.

Going to change them at reasonable intervals? The cheapest "copper" plugs you can find.

Never want to change them ever again? Iridiums.

Platinums are a waste. They take more energy to light off than either Iridium or standard plugs, and their only benefits are wear and anti-fouling. In a properly running engine standard plugs work best.

And Bosch +4's are a joke.

y_p_w · Jun 23, 2005

quote:

Originally posted by Jon:
The answer: it depends.

Going to change them at reasonable intervals? The cheapest "copper" plugs you can find.

Depends on the car though. If replacement is a PITA (V or boxer) then longer life plugs make a lot of sense (esp if you're paying someone to change them). If it's an inline engine, then standard copper core, nickel-alloy electrode plugs are fine.

quote:

Never want to change them ever again? Iridiums.

Platinums are a waste. They take more energy to light off than either Iridium or standard plugs, and their only benefits are wear and anti-fouling. In a properly running engine standard plugs work best.

Up to the point where erosion and/or oxidation make the standard plugs harder to fire up. I used to have them changed every 15K miles or 1 year on my '89 Integra. It was a breeze to replace them. Pop the wire boot. Pull the plug. Put new plug in with torque wrench and locking extension. I've got a WRX now. Now it's: remove air filter box, remove washer fluid reservoir, etc - hope you don't lose anything.

quote:

And Bosch +4's are a joke.

Duh.

kcirdnek · Jun 23, 2005

I have a 1996 Chevy Impala. Getting to the plugs isn't that much a pain, I just have to jack the car up. But, I do want something that is going to last for a couple of years(just in case I do fill kind of lazy in one year about changing them). Since reading this forum and our Imapala forum, I've been finding out that I have been using a couple of bad parts that I though were fine.

I read a post somewhere saying that the Iridiums don't have a long life. Is that true or not?

VaderSS · Jun 23, 2005

Go with the Stock AC Delcos or the Autolite APP 104s The 106s run a bit hotter than stock and can cause knock retard. I've run the stockers and the APP104s out to 50k, and they both looked like they had another 50k left in them. Make sure your APPs are nickle plated though. The old ones were blued steel and did not last as well.

Timothy Ferguson · Jun 23, 2005

I love my Bosch Platnium +4 plugs. I have been great gas milage and I have checked them every year now for two years. They are great. I guess like everyone says it all depends on the car or the environment that it is in. I don't drive that much or that far all depends how you look at it. I don't think they are crap.

y_p_w · Jun 23, 2005

quote:

Originally posted by kcirdnek:
I have a 1996 Chevy Impala. Getting to the plugs isn't that much a pain, I just have to jack the car up. But, I do want something that is going to last for a couple of years(just in case I do fill kind of lazy in one year about changing them). Since reading this forum and our Imapala forum, I've been finding out that I have been using a couple of bad parts that I though were fine.

Bosch may not be that bad. I just don't think their platinum design is suitable for use without frequent checking for electrode erosion. NGK or Denso long-life plugs are generally ones that you can put in and forget until the 60/100K miles change period.

quote:

I read a post somewhere saying that the Iridiums don't have a long life. Is that true or not?

I think Denso might have a "racing" iridium plug meant for a short change interval. Iridium has an extremely high melting point and should last a long, long time. It's also hard to fabricate with that high melting point.

Jon · Jun 23, 2005

All things being equal, Iridium will outlast anything. In my '92 Buick Roadmaster (350 cid), I changed the plugs at 40K intervals and they looked barely worn - I could probably have changed them at 80K intervals. At 300K the engine still runs great.

I would guess that 30K miles on a set of basic plugs would NOT be a problem. There will always be those that subscribe to the "more expensive is better" theory but there is a point of diminishing returns and with spark plugs there isn't hardly one at all. No mileage difference, and if you are going to change them at 20-30K miles, no life or performance difference either.

Rhymingmechanic · Jun 23, 2005

The NGK's you listed look like the numbers for my '01 Chevy pickup. It came stock with the 7862 Laser Platinum, and they looked fine at about 40k miles. The new AC Delco replacement is 41-985, an iridium plug gapped at .040 instead of .060.

pmwalter · Jun 23, 2005

Here is an excerpt from densoiridium.com:

Q. How long will Iridium Last?
A. Iridium use represents the most significant technological advance in automotive spark plug manufacturing, since platinum was introduced in the early eighties. As vehicle manufacturers produce increasingly complex and efficient automobiles, there is a greater need for long-life plugs that can tolerate leaner fuel mixtures and improved combustion processes. DENSO has responded to this need by developing its Iridium alloy, originally for OE applications. For example, many newer Lexus’ and Toyota models carry an ultra long-life Iridium plug variation (.7mm with platinum tipped ground) that is capable of up to 120,000 miles of service. DENSO Iridium Power plugs, with their .4mm center electrode, have been developed for performance applications. Because gradual wear will “round-off” firing points over time, the concentrated firing power and voltage requirement benefits will be reduced. For this reason, DENSO advises replacement after 30,000 miles.

See that 30K part?

y_p_w · Jun 23, 2005

quote:

Originally posted by Jon:
All things being equal, Iridium will outlast anything. In my '92 Buick Roadmaster (350 cid), I changed the plugs at 40K intervals and they looked barely worn - I could probably have changed them at 80K intervals. At 300K the engine still runs great.

I would guess that 30K miles on a set of basic plugs would NOT be a problem. There will always be those that subscribe to the "more expensive is better" theory but there is a point of diminishing returns and with spark plugs there isn't hardly one at all. No mileage difference, and if you are going to change them at 20-30K miles, no life or performance difference either.

I'd think most of the time, the plug gap will be out of spec and the edges will have rounded off by 30K miles. But when a standard plug is relatively new, it'll work at least as well as the more exotic plugs.

I've taken a look at my Subaru warranty booklet. Resistor spark plugs are actually covered under the emissions warranty, which is 3 yrs/36K miles federal, and 3 yrs/50K miles California. I suppose emissions warranty is one main reason why so many cars come with long-life plugs these days.

I'm pricing the NGK PFR6G plugs for my WRX. I think they're in the $12-18 range depending on source.

y_p_w · Jun 23, 2005

quote:

Originally posted by pmwalter:
Here is an excerpt from densoiridium.com:

Q. How long will Iridium Last?
A. Iridium use represents the most significant technological advance in automotive spark plug manufacturing, since platinum was introduced in the early eighties. As vehicle manufacturers produce increasingly complex and efficient automobiles, there is a greater need for long-life plugs that can tolerate leaner fuel mixtures and improved combustion processes. DENSO has responded to this need by developing its Iridium alloy, originally for OE applications. For example, many newer Lexus’ and Toyota models carry an ultra long-life Iridium plug variation (.7mm with platinum tipped ground) that is capable of up to 120,000 miles of service. DENSO Iridium Power plugs, with their .4mm center electrode, have been developed for performance applications. Because gradual wear will “round-off” firing points over time, the concentrated firing power and voltage requirement benefits will be reduced. For this reason, DENSO advises replacement after 30,000 miles.

See that 30K part?

But their long-life iridium plugs have a 120K mile replacement interval.

Elroy the Unique · Jun 23, 2005

quote:

Originally posted by pmwalter:
Here is an excerpt from densoiridium.com:

Q. How long will Iridium Last?
A. Iridium use represents the most significant technological advance in automotive spark plug manufacturing, since platinum was introduced in the early eighties. As vehicle manufacturers produce increasingly complex and efficient automobiles, there is a greater need for long-life plugs that can tolerate leaner fuel mixtures and improved combustion processes. DENSO has responded to this need by developing its Iridium alloy, originally for OE applications. For example, many newer Lexus’ and Toyota models carry an ultra long-life Iridium plug variation (.7mm with platinum tipped ground) that is capable of up to 120,000 miles of service. DENSO Iridium Power plugs, with their .4mm center electrode, have been developed for performance applications. Because gradual wear will “round-off” firing points over time, the concentrated firing power and voltage requirement benefits will be reduced. For this reason, DENSO advises replacement after 30,000 miles.

See that 30K part?

Go with the AC Delco RAPIDFIRES. This is GM's Performace Platinum Plug. They have a tapered Platinum Pad on the center electrode, and a nickel silver alloy on the side electrode (silver a great conductor).

You know these will be a quality part for your appliacation because it is AC Delco. They have minimum life rating of 60K (100K likely due to the platinum).

You can buy these at Autozone.

y_p_w · Jun 23, 2005

quote:

Originally posted by Elroy the Unique:
Go with the AC Delco RAPIDFIRES. This is GM's Performace Platinum Plug. They have a tapered Platinum Pad on the center electrode, and a nickel silver alloy on the side electrode (silver a great conductor).

You know these will be a quality part for your appliacation because it is AC Delco. They have minimum life rating of 60K (100K likely due to the platinum).

You can buy these at Autozone.

These don't seem to be like the original Rapidfires, which weren't platinum. They had a center electrode with a somewhat tapered and serrated edge to the center electrode.

There are some strong indications that original equipment ACDelco platinums are relabelled NGKs.

Looking at these newer Rapidfires, I question whether they can go 60K miles without a platinum tip on the ground electrode. Pure silver is the most conductive metal available (copper is second), but a nickel-silver alloy is hardly a superior conductor. Alloys in general are poorer conductors than pure metals. How conductive the metal isn't as important as its resistance to oxidation or erosion. There's usually a resistor in the plug that's orders of magnitude greater than the combined resistance of the tip, core, and contacts. Not to mention the effect of the oxidation.

kcirdnek · Jun 23, 2005

So, basically, this is an argument about which metal conducts better and withstand heat longer?

y_p_w · Jun 23, 2005

quote:

Originally posted by kcirdnek:
So, basically, this is an argument about which metal conducts better and withstand heat longer?

Withstanding heat - to some degree. Which metal conducts better - not really. Like I said, what metal conducts better means little when there's a big resistor in the plug and resistive plug wires are used that are several thousand times more than the difference between the resistance differences of the metals used in the electrodes. Not to mention you're trying to drive current across air. It's not that nickel, silver, nickel-silver, platinum, iridium, etc is a better conductor. They're probably all decent conductors, but electrical conductivity is meaningless compared to the resistance to erosion and oxidation, or mechanical strength.

If you want a truly long lasting plug, it's going to need two platinum or iridium tips that resist erosion and oxidation. If accessing the plugs is not a problem, standard plugs replaced more often will work just as well.

I'd recommend an NGK or Denso double platinum or iridium plug. That means the NGK "Laser Platinum", NGK Iridium IX, or Denso Iridium. Have you thought of the Denso PT16EPR-L13 (5070) double platinum? You should be able to find those at Autozone for under $10 each.

http://www.ngksparkplugs.com/apps/car_truck_suv/results.asp?engineid=4904
http://www.densoaftermarket.com/onl...sprk&year=1996&make=CHEVROLET&model=IMPALA+SS

punisher · Jun 23, 2005

The foolproof way- Look in the owners manual or the underhood sticker and run what the manufacturer reccomends. Hard to go wrong that way.

kcirdnek · Jun 23, 2005

Well, we are not talking about my car anymore. I know what I am getting now. We are just talking about plugs in general now.

I have another question now: Which Iridium plug is better? Is it a preference? Is there one better than the other?

The Denso has more surface area which make sense to be better:

http://www.densoiridium.com/patentedtechnology.php

But, I know A LOT of people like NGK for some reason.

Winston · Jun 23, 2005

Re: which Iridium is better, the NGK has a platinum tip on the ground electrode while the Denso does not. This would make me think the NGK would last longer. However, the OEM plugs for my car are Denso Iridium with a change interval of 105k miles.

As far as my experience with NGK double platinum I used them for 90k on one car while the recommended change interval was 60k miles. Some of the chunks of platinum that should have been on the ground electrode were worn off. However, I did not notice any difference in performance.

Spark Plugs

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