I noticed that my Toyota Maintenance Schedule seemed to indicate that my 2004 Camry should have the spark plugs replaced every 30K miles.
The manual says the spark plugs are iridium which I thought lasts a long time. I was looking in a 2009 Corolla maintenance schedule and it says to change spark plugs at 120K miles. The Corolla has iridium spark plugs also. So I started doing research on the internet.
I read many posts on the internet with people confused about when their 2002-2006 Toyota spark plugs should be changed. And read many posts that the Toyota service people said change the plugs at 30K miles. I found a Toyota spark plug pdf for 2011 that shows late 1990s and newer models of cars, trucks and suvs and about what spark plugs are used. It mentions iridium spark plugs last to 120K miles.
I called Toyota to ask what was the correct spark plug change interval. I told the person about the conflicting information. She just repeated that what was in the Toyota Maintenance Schedule was correct. I said she was not helping and so she transferred me to a higher level support person. I again told the person about the conflicting information. He put me on hold and did some research.
He came back on and said, do you see the "Replace spark plugs (ECHO)" listed in the 30K miles or 36 months page? I said yes, well that means it is just for the Echo car. I said, oh right Toyota made a car called Echo…before when I read ECHO I thought it was some sort of abbreviation. He said see at 120K miles page, that it just says "Replace spark plugs", that is for all cars.
Toyota confused not only the customers, but the dealer service people as they are recommending 30K mile replacement for 120K mile spark plugs because of the poorly written and cryptic statement. Why didn't they write "Replace spark plugs (Echo Only)"? Much more clear. I hope this helps someone, please post a comment if it helped you.