Jeeves said:
Platinums are bad and iridiums are overkill.
The NGK Coppers (3230s if I recall) are just fine, especially for a stock turbo motor, the gap will have to be different for an N/A Motor however.
First, this is a NA motor, not a turbo motor.
Further, why do you state that platinums are bad? Both sets original Denso platinums I've had it in worked flawlessly for 60K and 66K miles. Never a hint of detonation or missfires, always started easily. When pulled, they look like a poster child of the perfectly working spark plug.
And from researching spark plugs the last few days, I understand that not all platinum plugs are created equally. Various amounts of platinum are used and different locations, some with platinum just on the center electrode, some on both the center and ground electrode. A few with platinum on the center electrode and something exotic on the ground electrode.
Then there are the electrical and thermal conductivity characteristics of various metals used. Copper is a good thermal and electrical conductor, but poor on wear characteristics. Platinum have great wear chracteristics, but are not that good at electrical and thermal conductivity, however, it must be good enough since the previous platinum plugs worked well. Maybe in a highly boosted turbo or nitrous application the copper has an advantage because of heat issues, but I don't think a blanket statement that "platinum plugs are bad" is justified, IMHO.
