I'm coming up on my 6th year of ownership in December on my 2020 ES350 UL. I have the 3.5L engine and according to the owners manual the spark plugs should be changed at 60,000 miles or 6 years. I always far exceed the owners manual service schedule but was wondering what others have done for the spark plug replacement. I know many engines have 100,000+ mile plugs so this seems like a short change interval. I'm wondering if they recommend changing them because of emissions, fouled plugs or if they really are worn out at this point. I only have 36,000 miles on my car. What would be the improvements of changing the plugs at this interval? Better reliability, better gas milage, better emissions. I don't mind spending the money to have it done if its really worth it. I know this isn't cheap though. before someone suggests doing it myself that's not an option for me and yes I have watched the YouTube videos on how to do it. I've seen prices to have this done at the dealership between $350-$800 reported at various forums.

 

I have an 05 Toyota Solara that I didn't change the plugs until 100,000 miles. The old plugs still looked clean. No crud and can still come close to looking like new.
I didn't feel any power increase or better fuel efficiency. I did feel a little smoothness on the way the car revved and idled. Not by a lot but I could feel it.

 

The danger and downside of changing plugs on older cars (which yours is not) is that the plastic tabs from the connector and coils, they get very brittle. If you press the tab and pull, often you'll hear and feel the dreaded plastic crunch.
I am ghetto so I used zip ties.

 

What was the interval Toyota recommended changing the plugs? We don't have exactly the same engine.

 

I did mine at about 108K kms or close to 68K miles, and documented it here:

https://bobistheoilguy.com/forums/th...gr-fks.384331/

It took me about 2.5 hrs in my garage. I setup an outdoor table beside the car with a laptop and went step-by-step following the CarCareNut’s YouTube video. I also had to buy an inexpensive tool: magnetic spark plug socket:
I bought the plugs and gaskets from the dealer too, and cleaned the throttle body while I had everything apart. It wasn’t too difficult, I just went slow and careful. I could have bought the plugs from rockauto for a bit cheaper, but shipping to Canada is not cheap.

As you can see from the pics in my bobistheoilguy post, they didn’t need to be done. I think the manual recommends they get done for emissions compliance. I am currently at just under 170K kms and don’t plan on doing them until maybe 220K or 240K. I didn’t notice any fuel consumption improvement or really anything else.

 

Lexus now recommends premature plug changes because of emissions warranty regs from the government. It’s not the plugs that fail; it’s a non-technical paperwork/government issue.

Modern Iridium or (better yet, new tech from NGK) Ruthenium plugs will happily run 150k miles, even longer according to some Japanese engineering studies. In the JDM, they are pushing to move the change interval further OUT to recognize reality. So do what you feel is right - follow the engineering and go to 125k safely, or play the paperwork game and change sooner. Thems the facts, enjoy. FYI, not changing the plugs will not void any warranty. For a warranty to be voided, a service or lack of has to be PROVEN to be the cause of an issue. This is the federal law per the Magnuson-Moss act of 1975. It’s been law for 50 years, despite what anonymous internet commenters would tell you.

 

That's least of your worries.
In an older car, you can strip the threads on the head that plugs screw into especially if the plugs have not been changed for a long time.

 

True. My friend has a IS350 that's been bricked a few years now because one of his plugs decided to take a vacation from the engine as he was driving. the plug won't thread back into the block. His theory (unproven) is that the prior owner must've tried changing the plugs himself and stripped the threads. Weird thing is he drove the car for 30,000 miles or so when he bought it (used) so even if it were true prior owner stripped it, not sure why it lasted so long. He has other cars so he hasn't bothered to fix it, but at some point he says he will get a used engine.

either way you always want to go extra slow and extra careful when doing the plugs. Ensure no debris in the threads, etc.

 

Yeah. Also no anti-seize on plug threads..They already come pre-coated.
Anti-seize burn over time and turn into carbon. Next time you try to unscrew it again .. Bye bye head plug threads.

 

Maybe a good one to let the dealer do even though they'll charge a kidney and your first born.

 

Why wouldn't he try a heli-coil before swapping out the engine?
I'd trust a good independent shop before I trusted a dealer.

 

Heli coil is the way to go and generally removing the head is best to installing.