GTcarz - Automotive forums for cars & trucks.

Alright this is how generally how i rate plugs.

platnuim- uses an oem design with an extended long life with good performance. In this instance i would say good performance at am OEM level. Also it depends on what kind of platnuim plug you are using. There is a Platnuim center electrode and platinum tab on ground electrode or just platnuim center section. Ones with just the platnuim center section are usually just long life, but not so much as for performance.

Iridium - uses an oem design, oe design replacement and high performance. these are good for forcd induction engines, but beware they are expensive. A forced induction engine is obviously higher maitence so beware that the plugs can hit your pockets.

Copper - uses an oem design, short life, can transfer heat better then many other metals used. These plugs are cheap and are good with high performance at the cost of shorter life. These plugs take heat very well incomparison to others and are a great candidate for forced induction engines, which are at the risk of more heat.

This is a bit of information i got from a NGK technical representative:

The concept of a “copper plug” is based on other manufacturers where they will use other metals for the core of the spark plug where ALL of the above listed NGK spark plugs have a copper core (which transfers heat much better than any other metal used). Even though they use a copper core doesn't mean the certain plugs electrodes both center and ground are practical for your paticular vehicle.

Once again it bares down to heat ranges as every vehicle is different.

As mentioned in the article by "overkill" the term plug indexing.I have used this many times and can see its effectiveness. Here is a quick link explaining what it is and why. Do some research and you will find many poeple doing it.

http://www.advanceautoparts.com/english/youcan/html/pht/pht20001001sp.html

http://www.hotrodders.com/forum/indexing-plugs-79782.html

Heres a good explination of spark plugs from a user called "overkill" from http://www. oqcgp. com . I share the same opnion as him and it also gives a bit more description on metals.

Which Spark Plugs Should I Run?

Give me a spark plug 101

A spark plug has two main tasks: to ignite the air/fuel mixture properly, and to remove heat from the combustion chamber to maintain an optimal temperature.

Platinum, some hear that word and think BAM these are premium plugs. What makes platinum different? Well the answer is in the design of a platinum plug. So lets start there.

A spark plug's firing task is to transfer electrical current or "spark" between a power and a ground electrode to ignite the air and fuel mixture. We want this spark to be powerful, to promote a nice clean burn of the mixture, as this will promote the best efficiency and therefore the most power. Now imagine two spheres electrically charged, hold them closely together and you'll see spark jump across it. Now try and separate them and you'll see the spark disappear. NOW try this with two sharp pointed electrical rods and you'll see you can hold them further apart and the spark will still jump between them. What does this mean? Sharp points will transfer the spark the most effectively. Ever notice the tip of the spark plug and how most platinum plugs are sharp tipped center electrodes?

Sharp tips are all well and fine, but thats a hot environment down there. Infact the biggest problem is withstanding the heat. A sharp center electrode will get very hot, this promotes easy ignition (less charge to spark the plug) and a clean running plug free of deposits, but try this with a standard copper plug and it'll melt! Platinum has a much higher melting point than copper which is used on the classic style spark plug, thus the tip can be sharpened like it is. Iridium is the new guy on the block; same thing, it has an even higher melting point, thus the tip can be sharp. Now a copper plug needs to have a wide body to disperse the heat over a larger area so its tip can run cooler. Now did that set off any light bulb on where that would be beneficial? If you said forced induction or nitrous applications, pat on the back! In applications where you want to minimize existing heat in the combustion chamber, platinum may not be a good thing.

Here is another stick in the spokes of the platinum bandwagon wheel: Platinum does not conduct electricity very well. Platinum was chosen due to its resistance to heat and erosion, however it conducts electricity about a third as well as copper. The new iridiums are an attempt to find a metal with similar heat and erosion resistance as platinum but better conductivity of electricity; however, iridium is still only about half as good a conductor as copper, iridium plugs are one of the best marketing tools for spark plugs today and nothing more in the authors opinion. Now this disadvantage of platinum is offset to an extent by the ease of firing that platinum plug design offers, with its sharp pointed tip. Whether a copper plug can produce as much spark energy with a smaller gap however, than a platinum counterpart with a wider gap, is a good point of debate. The author’s viewpoint is yes.