When I first bought the XK, I was kind of surprised at 30k mile plug changes in the manual. That's different in a world of 100,000 mile tune-up engines.

But... after reading about the 4.7L engine on sites such as this: http://www.allpar.com/mopar/47.html I see it's actually a pretty high performance engine at that. I can see how plugs get eroded after 30,000 miles. It's almost like being back in the muscle car era again.