No matter what the heat range numbers say for a particular plug ( or comparing different brands of plugs), the farther the porcelain and tip is from the plug housing, the hotter it is going to run. The hotter it runs, the more prone to detonation it is going to be. Just because you can't hear it or see aluminum flecks on stuff, or melted ground straps, etc, doesn't mean your engine isn't running in some degree of detonation. Long before there were knock sensors on engines, I worked in a knock lab ( late 60's ) for a large oil company. An eye opener regarding engine detonation. I wouldn't be surprised if over half the build claims I see on this sight ( running outrageous CR's on pump gas )are running in some degree of detonation. It's just not enough to see / hear or to break stuff - but can be enough to negatively affect performance - and definitely enough to shorten engine life. Hence, knock sensors on all late model performance cars from the factory. KNOCK KNOCK, WHO'S THERE -----------. Hey Thumper, how's tricks?