iridium is a platinide, much like rhodium and , wow! platinum!
this means it has a melting temperature well in excess of 1500 degrees celcius.
its hard too boot. makes nice jewellery and laboratory equipment
they use it in specific style spark plugs for a reason. length of service intervals.
they dont wear out (as fast as standard plugs)
youll find them in the REAR CYLINDER BANK ONLY on a car such as a mitsubishi magna V6. why? cause they designed the silly thing so you have to remove the entire inlet manifold to change the plugs! this becomes a major service, and as such, is around about the 150,000 to 250,000 km mark. the front row of cylinders,on the other hand, are easily reached, so use standard plugs.
a standard plug should be changed every 10,000 or so.
so what does this mean?
well, considering platinum sells for twice the price of gold, and that iridium is even more expensive, the plugs are very expensive.
they make absolutely no difference to spark temperatures.
again?
THEY MAKE NO DIFFERENCE TO SPARK TEMPERATURE.
this is a function of coil strength, not plug type. more current/voltage makes a hotter spark. not an expensive spark plug.
combustion temperature is a combination of compression ratio, fuel type, and fuel mixture. the spark has no bearing on combustion temperatures.
other than to get it to burn in the first place. that bit helps.
the average lifetime of a HT seems to be less than the average lifetime of a standard plug....
so why spend all your dollars on a silly plug?
oh yeah. iridium is hard to re-gap. you arent meant to.
(yeah yeah, they arent that expensive but you get the idea now, i hope...)