Spark Plugs: NGK IX Iridium v. NGK Double Platinum

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How long does the NGK IX iridium spark plug last compared to their double platinum spark plug? I noticed that many OEM spark plugs are the NGK double plats and they say it lasts 100k miles. Just wondering how long the IX iridiums last in comparison, seeing as how it has a finer electrode (0.6mm), but iridium is a stronger metal...any opinions appreciated, thanks!
 
I just got a price on the OEM Honda Civic plugs for a 02 1.7L.Napa quoted $21.94Can. a plug my cost!
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I'll give you some examples:

NGK TR55 = Regular Copper Plug

NGK TR55GP = Single Platinum Plug

NGK TR55IX = Single Iridium Plug

NGK PTR4B15 = Double Platinum Long Life Plug

NGK ITR4A15 = Double Iridium Long Life Plug

Note: The center Iridium electrode is a fine wire because Iridium itself does not conduct electricity as well as copper; therefore the diameter needs to be made smaller to make up for the increased resistance to flow, but being that it's such a tough element, it can be made thinner.
 
Chuck - You are not really going to go 100,000 miles without pulling your plugs, are you? I just couldn't do it.
But iridium conducts better than platinum [actually, steel conduct better than platinum, but doesn't last].
Fine wire is a great idea, but don't expect a performance difference from irid to plat - a good heat range is more important.
 
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Note: The center Iridium electrode is a fine wire because Iridium itself does not conduct electricity as well as copper; therefore the diameter needs to be made smaller to make up for the increased resistance to flow . . .




That doesn't make sense to me, since resistance would increase as the cross-sectional area of the conductor decreases. I think the resistance of the conductor is negligible compared to that of the gap anyway.
 
The copper is in the insulator, not the tip. It is not exposed to the combustion chamber, or firing, at all.
You can have a copper plug that is steel, platinum, or iridium tipped.
 
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Note: The center Iridium electrode is a fine wire because Iridium itself does not conduct electricity as well as copper; therefore the diameter needs to be made smaller to make up for the increased resistance to flow . . .






That doesn't make sense to me, since resistance would increase as the cross-sectional area of the conductor decreases. I think the resistance of the conductor is negligible compared to that of the gap anyway.




It's real simple, if the center electrode of the Iridium plug were the SAME size as a copper center electrode, the resistance would be way up there because Iridium is not any where near as conductive as copper. That goes back to the principle of shorter wires having less resistance than longer wires of the same diameter.
 
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Note: The center Iridium electrode is a fine wire because Iridium itself does not conduct electricity as well as copper; therefore the diameter needs to be made smaller to make up for the increased resistance to flow . . .



No, you are confusing length with width. Assuming the lengths to be the same, to get better electrical flow you would want to increase the diameter. Just like putting water through a hose.


That doesn't make sense to me, since resistance would increase as the cross-sectional area of the conductor decreases. I think the resistance of the conductor is negligible compared to that of the gap anyway.




It's real simple, if the center electrode of the Iridium plug were the SAME size as a copper center electrode, the resistance would be way up there because Iridium is not any where near as conductive as copper. That goes back to the principle of shorter wires having less resistance than longer wires of the same diameter.


 
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How long does the NGK IX iridium spark plug last compared to their double platinum spark plug? I noticed that many OEM spark plugs are the NGK double plats and they say it lasts 100k miles. Just wondering how long the IX iridiums last in comparison, seeing as how it has a finer electrode (0.6mm), but iridium is a stronger metal...any opinions appreciated, thanks!




Chuck,

I use the NKG Iridium IX in my 93 Civic, It runs great. I change them out every 50,000 miles, don't forget to use plenty of anti-seize on the threads.

Harry
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How do your spark plugs look at 50k? I'm hoping to get 60k out of mine without sacrificing gas mileage or performance...simply cuz I'd like to bundle the spark plugs with all the other 60k maintenance items.
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Note: The center Iridium electrode is a fine wire because Iridium itself does not conduct electricity as well as copper; therefore the diameter needs to be made smaller to make up for the increased resistance to flow . . .






That doesn't make sense to me, since resistance would increase as the cross-sectional area of the conductor decreases. I think the resistance of the conductor is negligible compared to that of the gap anyway.




It's real simple, if the center electrode of the Iridium plug were the SAME size as a copper center electrode, the resistance would be way up there because Iridium is not any where near as conductive as copper. That goes back to the principle of shorter wires having less resistance than longer wires of the same diameter.




That makes no sense at all. The copper is larger because it is sacrficed in the spark event, and wears away. It needs to be larger to have an acceptable service life (and its inexpensive). The Iridium is smaller because it does not lose as much material during a spark event, and will last much longer. It is far too expensive to have a large Iridium wire...especially when a small one will give the service life you need.

As cross section of a wire increases, resistance goes DOWN! A larger in diameter iridium wire will have a lower resistance per unit length.
 
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