Changed spark plugs at 97K

I was refering to counterfeit plugs....

 

If it is fake, it is probably made of copper or some other cheap material and just won't last as long. The scammers are quite clever to make plugs that work.

Just write down your spark plug install mileage. If you get engine misfires at around the mileage of a copper plug, then you have a general idea of the culprit. If your plugs last past 100,000 miles then you got real iridium plugs.

I bought a set of NGK iridium plugs for my Corolla from RockAuto back in 2008 that lasted 120,000km. I bought another set of Denso iridium plugs for my Prius for $10/each from RockAuto in 2016. I later learned about fake plugs last year.