I changed my plugs yesterday afternoon to autolite platinums. The stock motorcrafts had different #'s for the passenger side and driver side. The driver side looked like they were all replaced but the passenger side looked quite worn. Did Ford change the #'s of the plugs? Also, why would someone change only 4 of the plugs?

 

original owner of my 98, never heard that they changed plug #'s replaced all my plugs twice(bad advice on the first set) but the #'s were the same.