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Can anyone please advise on which is the preferred NGK replacement plug; the copper or iridium? Thank you.
 

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If you don't mind changing your plugs every 15,000 miles or so go with the BKR7E vPower copper plugs. If you don't want to change the plugs as often then go with the NGK BKR8EIX iridium plugs. The copper plugs are cheaper per mile and perform better at low RPM but don't last as long.
 

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If you don't mind changing your plugs every 15,000 miles or so go with the BKR7E vPower copper plugs. If you don't want to change the plugs as often then go with the NGK BKR8EIX iridium plugs. The copper plugs are cheaper per mile and perform better at low RPM but don't last as long.
Great to see an informative, thorough answer made simple and unbiased, advising the benefits of both types. Often people just give a one word answer with no substance to support the claim =)
 

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Great to see an informative, thorough answer made simple and unbiased, advising the benefits of both types. Often people just give a one word answer with no substance to support the claim =)
Don't assume there is no bias in any answer you get on any forum.

Just to be clear, NGK does not make copper spark plugs. Standard NGK V-Power plugs have a copper core (just like every spark plug including platinum plugs), and they use Nickel for the electrodes. Nickel is not the best conductor. It is a much better conductor than platinum, but not as good as iridium.

I doubt that there is anyone on this forum that knows spark plug design better than the NGK engineers. Here is what NGK says about spark plug materials.

“Copper spark plugs” is a term mistakenly used for a standard material spark plug. A standard material spark plug traditionally uses a nickel-alloy outer material fused to a copper core. Almost all spark plugs use a copper core center to conduct the electricity, jump the gap, and promote heat dissipation. However, as an outer electrode material, copper would not be a good choice, as it is soft and has a low melting point (resulting in a plug that would last minutes, not miles). Nearly all NGK spark plugs, including precious metals iridium and platinum, have a copper core. When one talks in terms of nickel alloys, platinum and iridium, one is referring to its durability, or how long a spark plug will last before it needs to be replaced. However, when one talks about copper, he or she is referring to its ability to conduct electricity that is needed to fire across the gap and ignite the air-fuel mixture."

https://www.ngksparkplugs.com/about-ngk/spark-plug-101/5-things-you-should-know-about-spark-plugs

I have tried both the V-Power Plugs and the Iridium EIX plugs in my Cruze. I personally think the EIX plugs perform better. I believe that is because iridium is a much better conductor than nickel. NGK also rates the EIX iridium plugs as higher performance than both the standard V-Power plugs and the platinum plugs. Feel free to disagree with the NGK if you like.

Some people believe fine wire plugs do not perform as well as the massive conductor standard plugs. There is a lot of debate about this all over the internet. Here is a good article:
Spark Plugs - Fine Wire vs. Massive

It mentions an unbiased test: "RAM flight test data has shown fine wire spark plugs to be around 2.2% more efficient than massive electrode spark plugs."

If you want the longest life, and don't mind compromising a little power, stick with the OEM platinum plugs.

If you want better performance, try either the Nickel V-Power or iridium EIX plugs. I personally prefer the EIX plugs. Many people on this forum have tried both and prefer the V-Power plugs. In fact, there are people on almost every car forum will tell you that nickel v-power plugs are better despite what NGK says. These are all biased opinions.
 

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Do NOT put platinum plugs in a 1st Generation Cruze. The OEM plugs are iridium. My recommendation to OP was based on 100,000 miles driving my ECO MT on a combination of

OEM plugs (NGK IFR 7 series Iridium plugs - I don't know the exact model number)
NGK BKR7E vPower 4644
NGK BKR7EIX Iridium plugs
NGK BKR8EIX Iridium plugs

My assessment is that the BKR8EIX and BKR7E-4644 plugs perform almost the same. The problem is the 8EIX plugs only last about twice as long and cost three times as much. The BKR7EIX plugs are better than the OEM plugs but not as good as the 8EIX and BKR7E plugs. Thus my recommendation to go with the BKR7E if you don't mind checking your plugs every other oil change.

My recommendation, while potentially biased, was based on my own experiences with my 2012 Cruze ECO Manual.
 

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Do NOT put platinum plugs in a 1st Generation Cruze. The OEM plugs are iridium. My recommendation to OP was based on 100,000 miles driving my ECO MT on a combination of

OEM plugs (NGK IFR 7 series Iridium plugs - I don't know the exact model number)
NGK BKR7E vPower 4644
NGK BKR7EIX Iridium plugs
NGK BKR8EIX Iridium plugs

My assessment is that the BKR8EIX and BKR7E-4644 plugs perform almost the same. The problem is the 8EIX plugs only last about twice as long and cost three times as much. The BKR7EIX plugs are better than the OEM plugs but not as good as the 8EIX and BKR7E plugs. Thus my recommendation to go with the BKR7E if you don't mind checking your plugs every other oil change.

My recommendation, while potentially biased, was based on my own experiences with my 2012 Cruze ECO Manual.
OEM are iridium tip with platinum ground strap. Hence why they are long life and run terribly at low RPM.

The 8EIX ran...weirdly for me, so I stuck with the 7E-4644 plugs for the duration of my time with my 1st gen.
 

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I am currently running the 7EIX plugs. My Cruze is automatic, but these plugs provide much more consistent and reliable power than the OEM platinum/iridium plugs.

Personally, my main concern with the 7E nickel plugs is that they draw more current, which puts strain on the coils and has the potential to damage them. The coils in this car were designed to work with plugs that have a fine wire center electrode.
 

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I too run the 7E 4644 plugs. Have worked great for me. I get right at 30k miles out of a set and have to regap every 10k miles. I pay around $8 for a set of 4, versus almost 4 times that for the Iridium plugs. Car seems to idle and run so much better with the 7E plugs also. If I were not running these, I would probably just go back to running what came in it from factory, and replace every 60k miles.
 
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