Whichever model year the cutover was to non-waste-spark ignition, they went to high energy coils. The first coils were not, for some reason. Maybe a leftover part number from the old 318's & 360's? Anyway, that's why they had to use non-coated plugs (copper only) and change @ 30k miles. I know because I had one of those (MY 2007) and researched it.
If you have the newer model & ignition, they come with double iridium-tipped, narrow electrode plugs that burn clean for a long time. Members are reporting the life (as exhibited by tip erosion and arc flashover) is north of 100k miles. I concur there's no reason to pull sans rough running and/or fault codes.
There was a lot of debate what to replace with, seems to have settled on OEM spec, though buy direct from NGK instead of giving Mopar their markup. I was thinking of downgrading to platinum for lower cost, but there was some debate about change in resistance affecting ECM programming. Also, I see platinum erosion @ 100k, needs changing @ 50k.
I see no need for NGK's promoting their latest rare earth coated plug, ruthenium. NGK claims it provides better spark, with hi-speed ignition photos to prove it, and even longer life. For even higher cost, of course. What that translates to in the real world, I haven't seen. Would have to be better fuel mileage and/or power, for me to try them.
