From the Net
5.7 HEMI Misfires/Spark Plugs Longevity
OEM spark plugs don't last that long. They should be changed every 30,000 to 40,000 miles on Chrysler's 5.7 Hemi. And it can be a nightmare dealing with an ignition-related misfire, as the Hemi V8s have two spark plugs per cylinder. Plus, it will double the maintenance work, and a pack of 16 modern spark plugs isn't cheap.
