It's about time to change them... But like most of us at this mileage you quickly realize that the plugs still look surprisingly new after than many miles.
I always go by the Toyota maintenance schedule. So maybe get it done at next oil change. Some people exceed maintenance intervals, wait until there is a problem with the car, then try to figure out what is broken and agonize over what they should have done. You’ll have to change them eventually. If you DIY it’s cheap. Even many dealers don’t charge an arm and a leg. I’m assuming you also change all other fluids accordingly? You could also check and change PCV valve at same time. A failing PCV eventually can cause other problems so get it done too. Always get genuine plugs from local Toyota dealer parts counter. Don’t buy on Amazon. Once you change them you have peace of mind for likely the life of your ownership of the car. When I look at the car and see how little it costs to maintain, I’m amazed.
And.. don’t forget to change the serpentine belt. Toyota recommends that it be changed every 60k. My be overkill but … They are cheap. Often you can’t see that it’s cracking without removing it and by then you’ve already done the work of replacement. At 190k, mine looked fine until I pulled it and the underside was cracked badly. Prior owner replaced it at 120k. Not something you want to be surprised with.
Also want to look closely at the water pump and the belt tensioner pulley. Check for looseness or wobble, and for dry- noisy bearings. Maybe replace the tensioner pulley just 'because you're there. Posted via the PriusChat mobile app.
I may stall on ours. 3rd gen schedule is also 12 years or 120K miles (192k kms or something like that). We're coming up on 12 years this fall, but odo's only at 94K kms. I did pull them a few years back for a look and clean too. I'm thinking of leaving them to the California spec, 15 years or 150K miles IIRC. That'll sync with second round of coolant change, and will be more opportune for me, have the wipers and cowl off, coolant drained, do the plugs and good time to revisit..., the EGR.
It's called preventive maintenance for a reason. You don't want the car to start acting up in the middle of your road trip. Things get very expensive very quickly, when your desperate. Manufacturer's recommendations is simply a guide, and they are saying that those plugs are more likely to fail than to keep running efficiency at this point in their life span. Pick a convenient time to get the job done - preferably before a major road-trip... Good Luck
