Spark plug change at 125K for Toyota Sienna - worthwhile?


I have a 2004 Toyota Sienna with 124K that has been and is running perfectly as far as I can tell. It starts up easily and fuel economy has been steady since day 1. I am coming up on the recommended 125K spark plug change and wondering if this is worth the $500 my dealer charges for the job? I tend towards if it isn’t broke don’t fix it, but don’t want to penny wise, pound foolish. Any thoughts or recommendations will be greatly appreciated!

p.s. My dealer isn’t sure if the Denso plugs are platinum or irridium. They said if they are platinum, they would only be good for 60-80k while the irridium would be good for 125k. I am thinking that it would be worthwhile to buy the plugs myself since they aren’t sure. Does anyone know what would be the best plugs for my vehicle? Thanks!

Spark plugs wear out and need to be replaced. $500 every 14 years is a good deal. You might see if someone other than a dealer can beat that price. Check the owner’s manual for the recommended plugs.


Rockauto lists both platinum and iridium spark plugs for your vehicle.

I’d go with the iridium.


Denso SK20R11 is the correct iridium plug for your car, Advance Auto has them for $9.09 right noe with free shipping, you might find them cheaper online. I don’t know how hard to access the rear plugs are on a Sienna but there must be a Utube video. Any competent independent mechanic should be able to handle this job cheaper than the dealer.

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Why are you taking this to a dealer? Any independent shop could probably do it for less. And yes it is worth it. Not doing regular maintenance, never improves the reliability or longevity of anything.

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As a rule of thumb, if your maintenance schedule says to change the plugs, I see no reason to second guess the engineers who wrote that schedule.

If the maintenance schedule says to check the plugs at that mileage, however, it would be so costly in labor to pull the rear plugs on a minivan’s transverse-mounted V-6 engine that I’d either leave well enough alone until they should be replaced or I’d pull 1-3 of the front plugs to inspect them and stop there if I see nothing wrong.

I once made the mistake of dropping my motorcycle off with a new set of plugs at a local dealership service department, only to discover they never bothered to inspect them as instructed, and just swapped them out. I never went to them for service again after that, knowing the dealership owner’s son chose to ignore my instructions.

Knowing how much hardware has to be removed to get to the back spark plugs on a transverse-mounted V-6 minivan, there is a good chance you might not save money with an independent mechanic, and if you find an independent mechanic who gives you a quote that is significantly less, you might regret it later. This isn’t as simple as most spark plug change-outs.

If the OP can afford to spend the $500, I recommend getting it done at the dealership. If not, get a few quotes and go with the mechanic who seems the most competent, regardless of price.

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The question whether to have this piece of routine maintenance done is like asking whether there’s any reason that your Mom should get a dental checkup, since she’s not complaining about anything, and she’s getting old anyway so why invest a bunch of money on dental work if she’s probably going to die soon anyway?

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Yup. You’re paying for the drill-down, not the actual plug replacement. The front three are easy. The back 3 require more surgery to get to.

This is a DIY job if you’re interested, but you’ll need ratchet extensions and U-joints, and a lot of time and patience.

If there’s a valve adjustment scheduled for any time soon, you might consider having that done at the same time, as they’ll have to remove the same parts for that - why pay for the surgery twice?

Will you be keeping the Sienna for at least a few more years? If so, this maintenance item makes sense. If more incentive is needed, it might improve your gas mileage.

As for brand and type of spark plug, stay with exactly what is in there now. You do not need to be ‘upsold’ to a fancier plug. If more incentive is needed, the same plugs should give you another 125K with essentially zero risk of an unexpected compatibility issue (and the plugs are likely cheaper than the fancier plugs).

And regarding cost and DIY, you probably should not try this yourself unless you are reasonably comfortable with this type of work AND have some experience with what to do when things don’t go as expected. For example, are you ok with the idea that a plug in ‘the back’ might be really stuck, or breaks while you are trying to remove it?

Yeah might want to try a good independent shop if the dealer doesn’t even know what kind of plugs they are. I had my plugs, wires, and a four wheel alignment done all for around $200, including parts. The reason you don’t notice any problems with plugs in for 125,000 miles is that the computer keeps compensating for them until it gets to the point where it can’t compensate anymore. So more fuel used, more strain on the wires, coil, cat, etc. You haven’t had your air filter in there for that long too have you?


Thanks for the helpful replies. In the thought line of staying with the same type of plug that is in there now, the following link is to an OEM Toyota spark plug. It is listed with the following specs -

All resistor plugs with single ground electrodes feature patented U-goove design, resulting in a hotter spark
Platinum-tipped plugs are designed to last up to 60,000 miles before replacement
Toyota adds nickel and iridium to the platinum; this alloy helps make the spark plug strong and durable, while helping to prevent cracking
Genuine Toyota iridium spark plugs: The long-life, high-performance spark plugs

Does anyone have thoughts on these versus the Denso SK20R11 Iridium spark plugs? The 60k lifetime listed above for the OEM plugs seems to contradict the 125K recommended schedule for replacement in the manual, however they have worked great for 124K on my Sienna. Could going to a new plug vs the OEM increase the risk of potential problems? Thanks.

If you are relying on Amazon to direct you to the plug in your car right now, please stop.

As part of deciding who’s doing the work, ask if they will use exactly the same plugs as what you have now. If you are doing the work, please use a source better than Amazon.

And my apologies for the oversight, but changing the coil on boot(?) wires at least in the back three is probably a good idea. The front three are easily changed in the future if needed, and the back three can be saved for use in replacing the front three.

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Just me but I’ve never heard of a Toyota brand spark plug. I’m not an Amazon fan though but why would you not just go to a local dealer or quality parts store and buy the standard Denso or NGK plugs that came with the car? If you are not doing this yourself, then forget buying them from Amazon and let the shop get them. Interesting comments on them though. Appear to be quality plugs-like how can you tell the quality of the plugs by looking at them or the box they come in?

I had an old guy at the parts counter tell me that there seemed to be a difference in the quality of the AC plugs that were sold by DIY parts stores and those that supply mechanics. He said he had no way to verify it but seemed like it anyway from his experience. So I’ve always been a little leery buying plugs.

If you must buy them on-line, you can cut out the Amazon middle-man and just go directly to a Toyota dealer yourself. I bought mower bearings a while back and when I went to the vendor that popped up on Amazon, the bearings were actually cheaper than through AZ, plus shipping was free.

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Toyota’s website directed me to the OEM spark plug part no. and I did a search and Amazon had the cheapest price of the few websites I searched. Amazon’s website had the most information and that is why it was posted, not directed by to the plugs by Amazon. Thank you for mentioning about changing the coil on the boot wires and a good idea to do it while changing the back plugs.


ok. sounds like you are set.

if you are buying the plugs yourself, you might want to try and look at one of the front plugs to confirm what you have in the car before buying them.

Rock Auto is a better place to shop if you want to get parts online. They list Denso iridium plugs for your vehicle that run about $5 each.

Once caution, some shops will only install parts they supply. They won’t install customer parts at all. Others may be reluctant, but still go ahead and install customer supplied parts, but won’t warranty the work. A lot of shop though will install customer supplied parts with no complaints or restrictions. Make sure you understand which parts policy your shop uses. In any case, I concur w/the recommendation to use the exact same plug that’s currently installed. Why mess w/success?

The don’t fix it if it isn’t broken idea is good common sense. But there’s a problem with that approach regarding spark plugs. The tips of the plugs reside in a very nasty environment, the combustion chamber. Over time the threads on the tips of the plugs will accumulate carbon and other deposits from the exploding gasoline, high temperatures, and pressures. It’s really quite a horror show inside the combustion chamber. If enough of those deposits form on the plug’s threads, when the old plugs are removed the deposits can grind on and damage the corresponding threads in the engine. Often the engine threads are made from aluminum, which is a pretty soft metal. Damaged spark plug engine threads, that’s not something you want. So best to error on the side of replacing spark plugs too frequently rather than not frequently enough.

Thanks for the additional replies and good to know about the engine thread damage potential and about customer parts/warranty issue. I will check out Rock Auto and about the idea of checking out the front plugs to see what I have.
The OEM plugs information details lists a U-groove design - is this unique to the OEM plugs? and is it important?

Your car came with 125000 mile plugs. Why would you put in a 60000 mile platinum plug?

If you doubt you owners manual, pull an easy to get to front plug and buy the same kind.

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