Examining used spark plugs

[TheMAN]

so you're willing to spend hundreds of dollars to replace parts that basic preventative maintenance could've avoided this but you'll happily change the oil every 5000 miles? ok, got it

 

[SC Maintenance]

It's not

It's not how they look but how they perform. I would run the first set until I know there is a consistent performance issue and use that for a point of reference.

I "need" to change plugs in our Nissan 1.8 from 2010 with 150k on them but it is currently a non issue. I'll keep it in mind until I have an ignition related symptom which should be soon? Surely before 200k I would think.

An excellent way to ruin a cat, and your coils. I respectfully suggest this is a poor idea, you won't likely see a performance fail until you have done serious damage or ruined one of those components. The misfire CEL will also come on much too late because it will be intermittent for a long time in this scenario.

You could possibly monitor the misfire logs to see if you have misfires that are not enough to trigger even a pending code, but you still won't see the extra heat on the coils. If a coil fails 10 miles from home your cat will be in bad shape after driving home on 3. Sounds easier to change the plugs.