There is a misconception that a multi ground plug will produce mutiple sparks - this is not true, only the nearest electrode to the centre (i.e. currenty the longest) will spark, as that becomes worn, another electrode will become the longest and replace it as the sparking electrode.
I agree, that is true -- only the nearest electrode to the center will spark.
Q9. Do my multi ground electrode plugs outperform single ground plugs?
A9. In most cases, no. The additional electrodes disturb the flow of gases around the spark plug tip and performance may even be reduced. In addition, for high performance applications the additional metal within the combustion chamber will retain more heat and may be more prone to detonation/pre ignition.
I generally don't recommend multi-ground spark plugs as an upgrade, but certain vehicles do specify OE (Denso or NGK) dual-ground electrode plugs such as the 1995-up Toyota 5VZFE engines and 95-99 Mitsubishi Eclipse 2.0 Turbo. (Also of note are the triple and quadruple ground electrode plugs of the ancient Mazda RX7s
) Of note, the plugs with the worst feedback I hear are the Bosch Platinum +4s, especially when installed in Honda engines. People complain of misfires and unstable idling.
Thanks for sharing this interesting info. Reminds me of those Splitfire plugs (are they even still around?) I remember reading about legal issues related to unsubstantiated claims or something like that.