Due to the properties of Iridium, the spark plugs centre electrode can be made with a much smaller diameter than with platinum, Gold or gold palladium and copper/nickel types without sacrificing service life. The spark plugs potential difference is more concentrated at the tiny Iridium tip and hence less 'spark jump' voltage is required - this can be as much as 5,000 volts less than with standard plug types. Ignition is improved and less strain is placed on the ignition system. Benefits of improved ignition/combustion include better fuel economy, increased power/acceleration and especially better throttle response.
Of course, that's from this UK
spark plug page... not me.
