Just need to relieve some frustration on the topic of “the best spark plug”. I’m not a mechanic, but I have some sense and I know something about science. All the metals on earth have a specific rating of conductivity (the rating of resistance when carrying an electrical current). Of all 40 pure metals on earth, here’s the order for the best conducting metals used in spark plugs (I have complimented each listing of metal with a rating of 1 to 10 for conductivity performance):

#1 Silver (10/10 – Best electrical conductor on earth!)
#2 Copper (9.6/10 – Second best metal conductor on earth)
#3 Iridium (3/10)
#4 Platinum (1.5/10)

These are actual figures, and are not some arbitrary numbers that I made up. You can look at this website and see for yourself if you can read it, and have some science knowledge:

http://www.audusa.com/silver_has_the..._electrica.htm

To the disbelief of many people Platinum is by far the worst conductor of the four. But, conductivity is not the only determinant of spark plug choice. A spark plug should also have an adequate amount of resistance to oxidation and erosion (the ability to last long). These can also be rated:

#1 Iridium (Does not Oxidize!)
#2 Platinum (Very high resistance to Oxidation)

#3 and #4
Silver and Copper (Both have great resistance to erosion, but oxidize quite easily compared to platinum and iridium when exposed to common elements found in the combustion cycle of an engine).

The following sites explain the specific features of each element for those who are skeptics of the information I am providing:

Iridium - http://www.webelements.com/webelemen...xt/Ir/key.html
Platinum - http://www.webelements.com/webelemen...xt/Pt/key.html
Silver - http://www.webelements.com/webelemen...xt/Ag/key.html
Copper - http://www.webelements.com/webelemen...xt/Cu/key.html

So, with this brief explanation people can come to understand the benefit of each type of spark plug.

· Iridium plugs should last the longest, and are decent conductors.
· Platinum plugs are a close second in durability, but poor conductors.
· Silver is the best conductor, but tarnishes quite easily
· Copper, same!

You should choose the best plug should suit your needs. If you hate to replace your plugs, my assumption is to go with Iridium plugs. Platinum plugs are just a more expensive versions of Iridium plugs, but should serve no better. If you are out for the best performing plug, and want to lighten the load on your ignition system, go with silver plugs. But, Silver plugs are high maintenance. Copper plugs are almost as good as Silver, but a hell of lot cheaper.

Here is my overall rating of plugs (assuming they are made of pure elements):

High Performance:
1. Silver (Silverstone)
2. Copper (NGK)
3. Iridium (NGK)
4. Platinum (NGK)

Longevity and Practicality
1. Iridium
2. Platinum
3. Copper
4. Silver

Now, how important is the conductivity of a spark plug? Not as important as you think. Ignition systems are very powerful for a reason. They need to provide a CONSISTANTLY strong spark. A plug that remains in its original state over a long period of abuse can only provide this consistency. Lets be realistic here, and try to understand that we are not going to change our plugs at every oil change. I believe that Iridium plugs provide a more than adequate spark, and do not erode and oxidize. If you need a placebo to make you believe your car is going to perform better, go with Silverstove plugs. After all, they are made from the best conductor on earth! I personally choose to use Iridium NGKs in my Maxima, but hey, that’s my choice. The only exception here is if you are running the Sauce or Juice (NOS). You want a cooler plug to prevent detonation; go with Silver or Copper plugs. Plus, when running on the juice, you must perform maintenance often, so the longevity of the plug shouldn't be a factor.

In the real world it does not matter knowing all this information because we are going to test each plug and make our decision based on the real performance outcome. I’ve used a number of different plugs in all my cars, and never noticed a real difference in performance. I used to run a BMW (not my Nissan), and I would clock the exact same times, with NEW plugs, no matter what type I used. Over time the performance of any particular plug decreases at a fast rate. The most obvious difference between spark plugs is their longevity, and how long they can give me an equal amount of performance over time. Take a look at a Copper plug after 5000k, and look at an Iridium plug after 5000k, and you’ll know what I am talking about.

The only difference I can make in the performance of my plugs is by indexing them. This is to make certain that the plug provides the spark to the right spot in the cylinder (in respect to the fuel injector).

So which is the best plug for my Maxima:
The verdict is: NGK or Denso IRIDIUMS

 

thanks
i agree
i have denso iridiums too

 

one quick question, and i'm no scientist here: does the conductivity of the metal have that much to do considering the enormous resistance that must be overcome to make the spark leap through the air?

 

Not very important in this case. But, the less resistance the metal creates in the plug, the greater the plug's ability to break the barrier of resistance created by the molecules in gap. The point I was trying to make is that the conductivity of a plug is not the most important factor in the overall function of the plug. It's the plugs ability to perform consistently over time.

 

ppetruccelli,

Great post! I have known long before that Iridium was the best. Then again, it's my opinion and people will still say Copper/Platinum are better.


~limsandy

 

Excellent post. Thanks

 

ppetruccelli,

Just to let you know, there are 2 different type of Iridiums....double and single as is the case of the plats. The double means that the core and ground are made from Iridium while the single has only an Iridium core. Apparently, the numbers that start off are BKR....IX are single and thus cheaper than the double platinum. I read also that the only last as long as copper (around 30kmiles). I only discovered this after I bought mine .

Anyway, the guy that found this out posted the info in the 4th gen forum.

 

Thanks for the info. I wish I knew that. The double Iridium must be the OE laser Iridium. But, NGK promotes the IX as their best. Very Odd! I guess I'll have to periodically clean the ground. Too Bad.