I really dont know why buy here in Peru, all dealers (Volkswagen, Toyota, Nissan, and others) says we need to change spark plugs every 10,000kms (6250 miles). My last car used a bosh 4 electrode spark plugs, and were changes every 10,000km. Now im listeting about iridium and others saying you have more mileage to reach to a point to change the plugs.They say that plugs should be replaced at or near 100K miles. The original plugs .... ................. Plugs don't last forever and I think these plugs have served enough time in the car and needs to retire.
We have a website archeologist! A 9 year old thread in computer years is almost as old as Egypt!Change before 100000. They tell me that plugs can seize up and the at creates an issue. Change around 90000.