In my experience, there just isn't a swap-out mileage for (Denso) iridium plugs. They work brilliantly out of the box, with better starting, and just go on faultlessly forever. That's for a given value of forever, of course, but my ST4 has only had one set in the bike since I bought it on 3K miles and it now has 33K. Didn't need to buy four at that time; could have saved some money...andybaggies wrote: ↑6 years ago I've never bothered with (the price of) iridium plugs and have always used plain old NGK CR8EKs with no hassle what so ever. Even well beyond the recommended swap out mileage.
Nick