I have an 07 quad cab, 4x4, hemi, and a lifetime drivetrain warrenty. I try to most of the work myself and after talking to a few people, they said make sure I follow the manual so Dodge won't refuse any warrenty work. In the manual (and Chilton's) it says to change the plugs every 30,000 miles....Why? The guy at NAPA said to talk to the dealer. I know plugs wear out, but 30,000 miles? Any ideas? Most manufactures say the new plugs are good for 100,000 miles (give or take a few). Thanks