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Iridium plugs are supposed to add more power, reduce emissions, last longer, blah, blah, blah, but I have yet to hear of anyone who can supply me with any real life data.
Some people swear by them and tell of the transformative quality of them, others are less impressed.
I fall within the second group. I've run two iridum plugs now and have noticed no difference in power, economy or the ride.I was quite careful to measure the economy and noticed on avearge, no difference.
Others might disagree.
However, one thing to note an a single cylinder is that the spark plug is a critical item and I would much more prefer to swap the plug at every service for a brand new standard one than keep an iridium plug in place to the service change point.
Quite an opinionated point there but worthy of some thought.