Originally Posted by Jesse Open

Regarding iridium plugs and waste spark ignitions.

Waste spark sytems have two plugs, driven with a single coil, one has the center electrode at the positive end of the ignition coil secondary, the other at the negative. As a result the electrode erosion wear is unequal.

As cautioned by NGK:

" The use of nickel-alloy or single precious metal spark plugs in vehicles equipped with waste spark ignitions will result in more aggressive gap erosion and shorter spark plug life."

Not certain if the difference here will really be a factor, just thought you may want to be aware