It's not what I would call a definitive or authoritative site, but this chap seems to have some interesting things to say on the matter: http://www.picotech.com/auto/tutorials/ ... ndary.html in particular he states:brentp wrote:Related to reversed polarity across coil-pack plug plugs pairs, I recall seeing a discussion about single tipped platinum plugs wearing differently from cylinder to cylinder in a wasted spark setup, but searching recently I could not find any supporting information... ahh well.
DIS has its own drawbacks by having half of the plugs firing with an acceptable negative voltage, while the other half is fired by the less acceptable positive polarity. This will have the effect of pronounced plug wear on the positive fired plugs.
This system, because of its nature, will fire the plugs each revolution, instead of every other, and is known as a wasted spark system. This does not mean that the plugs will wear at twice the normal rate, as the wasted spark is on the exhaust stroke, and is therefore under no compression. If the spark plugs are removed after several thousand miles and examined, it will show that two of the plugs have relatively square electrodes, while the plugs that have been fired positive will have pronounced plug wear.
Maybe it would be worth swapping plugs on paired leads every few thousand miles?
TwoSheds
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