Extended spark plug intervals

Are you guys OK with the long(er) intervals for spark plug changes these days? Like 100,000 miles? Rocketman

Me? NO… But what do I know…I’ve only been playing with Spark Plugs for 33yrs now.

IMHO… Aside from electrode degradation over time (Which may be the factor that allows this longevity with harder more durable electrodes) What limits the time for the Steel Spark plug screwed into an Aluminum Cylinder Head is what happens to the threads over that long of a period of time. Ive seen plugs corrode and actually Bloom or Swell due to corrosion…which severely locks the plug into the cyl head.

Personally I ALWAYS install every single Spark Plug using Anti Seize compound…especially when the heads are Aluminum. I do notice however that I seem to be the only one… Plugs are or seem…to be installed Dry into the heads…regardless of materials used. Now I could be wrong about that but they seem to be installed dry.

I worry about getting plugs OUT of engines mostly… I can attest that a dry Steel plug installed into an Aluminum Head 5-7 YEARS ago will entertain the mechanic unlucky enough to be assigned to change said plugs. I’ve seen VERY ugly things happen when the Un-Initiated mechanic goes about changing these plugs…they usually take all the Aluminum threads with the plug when they simply try to “Run the plugs out” of the head.

Can a spark plug function for 100K miles? Probably …again due to harder more exotic electrode materials… Would I want a plug in my Heads for as long as those miles take to accrue? I think not… Not unless some sort of thread protection was used…and I cant fathom that nothing would be used in this instance to protect or lubricate those threads.


Personally I ALWAYS install every single Spark Plug using Anti Seize compound...especially when the heads are Aluminum. I do notice however that I seem to be the only one... Plugs are or seem....to be installed Dry into the heads....regardless of materials used

If you’re using NGK or Iridium plugs then you do NOT want to use anti-seize.


I don’t run plugs for 100,000 miles for similar reasons as @Honda Blackbird. I’d like to get them out without wrecking the head, especially on my Mustang with the notorious 3-valve V8. Those got swapped at 50K using an impact wrench to pop them out - gasp - with no broken plugs and went in with copper anti-seize. 50-80K is about all I can stand. They are relatively cheap at $8-$12 a plug for platinum or iridium but I used to change them at 10K with good 'ol leaded gas for $1 apiece. I don’t see any change in performance or gas mileage so the old ones were not degraded enough to notice.

But I don’t need any thread repair kits so I’m happy with this interval.

I got into the habit of changing spark plugs at around 50K. The thing that I’ve noticed is that the engine always runs better after new spark plugs are installed. The engine could have run with the old plugs for another 50K but it would have done so with diminished performance and at less fuel economy. New spark plugs are actually a bargain.

Spark plugs today are designed to go 100,000 miles or longer.

With the special coatings on the threads and with aluminum heads, there’s no chance for corrosion.

I’ve removed spark plugs from engines with well over 100,000 miles without any problems.

Back when spark plugs had just regular steel threads that where screwed into cast iron heads, they could get corroded into the head. Then they become forever plugs.

Also, some engines require that upper intake manifolds be removed in order to gain access to the rear plugs. So when you tell an owner of such a vehicle that’s going to cost $400-$500 just to check the plugs, they’re willing to wait until 100,000 miles before worrying about the plugs.

As long as the Check Engine light doesn’t come on with a misfire code, the plugs are fine.


Our Lexus was the first vehicle with Iridium plugs that don’t need changing til 100k miles. And it’s the first vehicle I’m extremely happy that I don’t have to change them earlier. The back 3 plugs are a royal pain to replace.

I agree with Tester most cars will do 100k on the plugs without issue. We see cars everyday with over 100k and don’t have any issues with removal.

Brand new perfectly operating engines might go 100,000 before needing a change… but once you change your second set you’re now talking about and engine with 200,000 miles.

I’m personally not comfortable with it. Even on new engines.

Anti Seize… Will be used by ME… ALWAYS…

The issue sighted earlier by Mike was as follows:
""" Issue:
Applying anti-seize to the threads of spark plugs that have a metal plating allows the installer to
mistakenly over-tighten the spark plug in the cylinder head; This stretches and fatigues the threads of the spark plugs, causing a much higher proba
bility that the plug will break during installation “”"

If THIS is the issue… I will gladly and happily laugh and IGNORE it promptly. Over tighten? A MASSIVE ROOKIE MANEUVER… One which I do not suffer from. Rookies? Perhaps, but this doesnt apply to me in the slightest of ways. I am also aware of how lubricant on the threads make the nut or bolt feel and Im well aware of the dangers or concerns. Far as I’m concerned some bolts like lube others like Loc-tite… Its either or with me…I hate a naked thread…but thats just me. Some rare instances dictate nothing to be added for contamination purposes and I would recognize those instances.

Every plug that touches my hand WILL HAVE some form of Anti Seize placed upon it.


Other than a hand inadvertently slipping and causing the problem, I’d say that any mechanic who breaks a spark plug due to the use of anti-seize should be in another line of work; maybe manually pounding spikes into railroad ties or something of that nature.

Besides, the fact that an engine appears to be running well and with no CEL illuminated does not mean that it’s running at it’s optimum.

I’ve often wondered if there’s a correlation between spark plug change intervals and complaints over O2 and converter problems.

I’ve never owned a car with the 100K plug change-out interval. So I’ve always changed plugs every 15 to 30 K miles per the recommendations in the owner’s manual. The kind of plugs my cars are spec’d for cost $2 to $3 each, so I’m not overly concerned about the cost of the plugs. But if the plugs cost $25 each and the spec was 100K miles, I’d probably consider keeping them for the entire 100K to save on the expense of buying new ones. I’d probably still remove them every 20-30 K miles for an electrode inspection though. I’ve always put a tiny amount of moly-lube (stuff I use to grease u-joints) on the threads as part of the installation process, and never had one stick yet, either in cast iron or aluminum heads. I always re-torque the spark plugs after the initial install, at around 500 miles.

My 05 Camry is 120K mile interval. I changed them at 100K miles, they looked good, but I was already there with the new ones sitting on my workbench. Per the instructions, I did not use anti-seize. It would take another 100K miles to figure I was right or not.

I have had no problems going 100k+ miles on double platinum and Iridium plugs. I have not had any get stuck in aluminum heads and I do NOT use anti-seize on NGK or Denso plugs, but I do on other brands.

I stopped using a torque wrench as well. I now use the old fashioned way of turning the plug the specified fraction of a turn after finger tight. This is now sometimes called torque angle which is also used on head gaskets now. It prevents over tightening of the plugs.

NGK and Denso plugs are already coated, so you don’t need anti-seize. Using it is a waste.

NGK and Denso recommends against the use of antiseize on their plugs.
Honda may choose to laugh at manufacturer recommendations, but I don’t. Perhaps it’s because I’ve participated in putting so many of them together. I’ve written the procedures and done the qualification testing, the validations, the accelerated life, the sand & dust, the temp cycling, the thermal shock, the impact, the heat/vibration… I have an appreciation for what goes into the design documents. I’ve even evaluated the results of torque values, and done a correlation in one case of application torque vs. breakaway torque for a specific application. I realize that manufacturer’s recommendations are not foolproof, but I respect them.

When the manufacturer recommends 7 to 15 Foot Pounds of torque on a spark plug installation then that might as well be grenade throwing territory.

Platinum and iridium spark plugs have been in use by vehicle manufactures for 25 years, if there was a major problem with 100,000 or 120,000 service schedule (besides the Triton engine) we would know about it by now.

Every plug that touches my hand WILL HAVE some form of Anti Seize placed upon it.

I had a guy working here that thought the same way. Unfortunately, I don’t think that way, and it’s my policy to not use anti-seize on spark plugs. Couldn’t get through to this guy though, and after repeatedly being asked and then told to stop using it on spark plugs, he still didn’t listen. I literally had to go through the shop and throw out all the anti-seize to make it clear that spark plugs are to be installed without it.

Other than the Ford Triton 3-valve plugs I don’t see problems with 100K or 120K spark plug service.

I haven’t run into ones that low, 7 to 15 ft/lbs. More typical is 18 to 21 ft-lbs.