sy112 said:
Thats what i got
I got this of another forum
Well, I checked NGK page (good thing is that I am Japanese, I can
read their Japanese web pages). They say they use Iridium alloy,
which has a higher melting point (2450 C, Platnium = 1770 C) and
good corrosion-resistance. Because of these reason, they claim
that they can make its central electrode thinner (0.6 mm diameter).
Also because the electrode is thinner, the electric field in the gap
becomes stronger than normal plugs (they didn't say platinum), requiring
lower voltage to cause a spark, so it is better for starting at low
temperature. They say this is more advantageous with high compression
engine (I believe 4.9 is supposed to be high compression, since
it requires premium gasoline..??).