Originally Posted By: GMBoy
I have a set of the Platinum TT's in my 3.6DI CTS. I'm happy with them. NGK is an excellent product but not the holy grail. Spark plugs are not exactly space age technology and even a cheapie copper plug does the job perfectly. Long life is the only main advantage to platinum and iridium plugs because more HP or fuel economy is not. Spark is spark for the most part!
Yes, spark is spark, but flame poprogation is another story. The Denso TT's are supposed to blend both flame kernel propragation and long life.
I have noticed a difference in driveability going from a double platinum plug to a iridium plug on my car. Not necessarily max power. With only 40K on the old plugs (NGK laser double platinum), I switched to NGK iridium. Now, if I need to pass someone, the transmission doesn't need to downshift, and I still be able to accelerate. Must be that finer wire electrode (.6mm vs 1.1mm) and the tapered ground electrode, allowing the flame kernel to spread better. Of course, with no platinum on the ground electrode, wear is compromised. But these plugs are cheap, so 40K miles changes aren't a big deal