TimeLord is correct. The original plugs should be OK at 28,000 miles. They're designed to go 100,000 miles. If one or more of the plugs is fouled, it's probably not the plugs fault, you may have another problem. If you do replace the plugs, I would suggest putting in the same brand and heat range as the originals unless you are racing, and then you would want to go to a colder running plug. waldig just posted a very useful thread on changing plugs. Good Luck https://www.crossfireforum.org/forum...ht=spark+plugs