Took my 2018 GS 350 F Sport AWD to dealer for 100K scheduled maintenance on 12 9 25. Service adviser said I need to replace spark plugs. Car has 99,600k on clock. Runs fine, starts right up, acceleration and gas mileage are same as when I bought car in September 2024. Car had 74k when I bought it. Lexus.com recommends changing at 120k. Looking for feedback. Thanks in advance.

 

There's other threads on this, with pictures. I think someone had close to 250k miles on original plugs and they still looked good.

 

Your OE iridium spark plugs will perform perfectly well beyond 150k miles with no degradation in performance or fuel mileage. The only reason to replace the spark plugs is for warranty of the emissions system, but I believe the emissions warranty is 8 years or 80,000 miles for major components like the catalytic converter and engine control module - and your car is beyond that mileage (if you meant 99,600 miles). I would not replace the spark plugs...

 

Plugs asked and answered, no real need to yet.

Important to change the PCV valve on these engines, though. Did they, or has it been done at some point? Easy DIY if not; $10 or less part.

 

Unless you are not handy at working on your own GS? You buy all 6 new plugs for like under $70.

 

Thanks. That's what I thought.

 

Thanks. Not sure if the PCV valve has been changed. I'm having serpentine belt replaced this week. I'm have my mechanic change PCV valve too.

 

It's true b*tch to get back there to where the valve is but I am an idiot because I completely forgot about this when I changed my plugs to maintain my emissions warranty..... the last plug on that side is literally right there and it's the exact same effort repeated to get to the PCV piece....annoying

 

When you DIY this job, a 19mm crow’s foot wrench can make all the difference. Here’s a whole set of metric ones at HF for $15, for reference. IIRC, the pcv valve takes a 19mm.

https://www.harborfreight.com/38-in-...EaAr4KEALw_wcB

 

Appreciate you champ! Thank you. I am going to knock this out soon as I pick this part up.