Iridium vs Platinum Spark Plugs
Aside from the very common copper spark plugs, there are two other options for most users; platinum and iridium plugs. Both types have the very same parts and construction, the only difference between iridium and platinum spark plugs is the metal used for the center electrode. As you may already have figured out, platinum plugs use platinum while iridium plugs use iridium for the tip of the center electrode. Iridium plugs cost more than platinum plugs, partly because iridium is a rarer metal than platinum, but also because it offers several advantages.
Iridium has a much higher melting point than platinum; with values at around 4400 and 3200 degrees Fahrenheit respectively. Iridium surely has an edge when you consider that gases are constantly being ignited in the chamber, exposing the spark plug to very high temperatures. The higher melting point means that iridium plugs can be made hotter than platinum plugs. Although hot plugs are not always desirable, it is preferable for city driving.
Another advantage of iridium over platinum is strength, with over 8 times the strength of the later. This essentially means that an iridium spark plug can take a whole lot more punishment before experiencing significant wear. A platinum spark plug is expected to last for 60 thousand miles before needing replacement while an iridium spark plug can go for 100 thousand miles or even more. The cost of the plug many not be such a significant argument, but the actual replacement can be an issue for some vehicles. Spark plug locations may be difficult to reach or require that other components be removed first. It would be more difficult if you do it yourself or more costly if you have it done in a shop.
Difference in performance would be relatively small if any between iridium and platinum spark plugs. If you are considering either as a replacement, the iridium plug is probably better since you do not have to change as often and you do not have to worry about the electrode prematurely eroding inside the combustion chamber and possibly leaving harmful deposits. But if you like changing plugs often, as new plugs would always perform better, using platinum plugs may not be a bad idea.
Summary:
1.Iridium and platinum spark plugs have different center electrodes
2.Iridium plugs have a higher melting point than platinum plugs
3.Iridium plugs are stronger than platinum plugs
4.Iridium plugs last longer than platinum plugs