I have 75000 miles on my 2008 Elantra, the maintenance schedule recommends replacement of Platinum coated spark plugs at 60000 miles and Iridium coated at 100000. How do you tell the difference? My last road trip of 1200 miles was just over 39 MPG.
I don't change them until I notice a change in engine performance. Typically lower gas mileage or a cylinder missing. Come to think of it, I can't remember the last time I changed plugs. I changed plug wires when a cylinder was missing and I could see a corona/arcing. Plug wires usually fail before plugs.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.