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These cars have coil packs so plug change is a 15-20 minute job...just pull the coil packs remove and replace plugs....and don't over think it..just tighten to snug and grunt once(give it a tad extra to lock it in) do not over tighten... seriously if you can't do plugs on this car in your sleep sell the dang thing haha

 

[flash240]

If you really think those plugs last 100k and shouldn't be replaced more than that....you got problems...why would you wait that long and risk failure...bad performance or worse breaking them.off when it's $50 for new plugs?....why wouldn't you change them before they get that bad?...if it's about money then maybe you can't afford a sports car?......
People just FYI....it's called preventative maintenance for a reason....surely no one here thinks the factory intervals are the best way to go on a sports car?

 

[flash240]

This is all very true my friend ....however the fact that people going the full interval are having seized plugs is proof enough that the intervals are too long...
Let's be clear....extended maintenance intervals are a convienance factor not best practice.....take oil for example....plenty of extended drain intervals oils out there....what they don't mention is that.for example with Mobil one15k oil,when your roughly half way there (7k miles)...the base lubricosity of the oil at that point is often no better than new conventional oil....that's unacceptable...that means that while you may be able to leave it in for 15k...it has long since lost the ability to protect your engine in the way new oil does. This a backed up with testing from Bob the oil guy....my point is extended intervals doesn't mean it's as good for your car to go that long....fluids especially lose the properties that provide protection after many many heat and wear cycles. I'm not surprised a Corolla plugs looked new at 100k...that motor has neither the power nor the rpm capability that the celca does....just saying....best practice is maintenance intervals based on your cars real world experience....if tour car eats plugs by 50k. Then change at 50k...don't wait for 100k just because that's some abitrary number the dealer wants you to go by....do the maintenance your car wants....not just what's called for...it will last longer.
Good discussion