I’ve read that if one uses anti-seize on spark plugs it lubricates them and can create inaccurate readings on a torque wrench when installing. I’ve never seen a standard recommendation for how much to reduce the torque, but I’m about to tackle a Subaru Outback, and Subaru recommends reducing the recommended torque by 1/3. Since the recommended torque is about 15 ft. lbs., that would mean only 10 ft. lb. of torque. Is that about the right amount of correction or would 12 ft. lbs. be OK without stripping anything? Just seems low to me, but I’m no expert.
spark plugs are always very little torque
12 ft lbs will be fine.
Just be sure when you install the plugs that you do so “gingerly” and allow the threads to start by themselves. Trying to force them is when they get stripped, and that’s as bad as (and often a precursor to) stripping them.
I’d sure like to know what kind of car we’re talking about and how often you change the plugs. I’ve never used anti-seize and I torque the plugs to spec. Unless I planned to leave them in for a really long time, I’d not bother with anti-seize.
I always use anti-seize and never torque plugs, In 50+years of doing it I have never stripped one or had one get loose. It doesn’t take much to seat them, I just hold the head of the 3/8 ratchet under the base of my middle fingers and turn.
I believe I mentioned it was an Outback. With the Subaru engine design it’s a bit of a chore to get at the plugs since you have to remove some other components. I’m thinking I’d be less inclined to change them as frequently as I do on my Camrys. I would think it’s better to not need anti-seize but still use it as opposed to finding out too late that things are stuck together.
NGK recommends NOT to use anti-seize on their plugs that have a special coating. Not sure about other plugs. I’ve been using NGK plugs exclusively for the past 20+ years.
Mike, that’s very helpful to know. I looked up one of their tech bulletins and they say that all of their plugs are made with a special coating and don’t need anti-seize treatment. I use only NGK, so it looks like I’ve been overly cautious and the stuff unnecessarily. That simplifies things considerably.
Everyone with an aluminum head SHOULD be using Anti-Seize. Steel in an aluminum head is a recepie for disaster. Ive also never torqued plugs…ever. I would call the torque value of plugs to be “snug” but again Ive been doing this for over 25yrs now so its hard to communicate this “value” to others…lol Just dont “hamfist” them in there and you will be fine… But PLEASE use anti seize…its little effort to prevent a MOUNTAIN of problems…so theres little argument against using it.
Blackbird
so theres little argument against using it.
Unless you use NGK plugs…
You do not use anti-seize on plugs that have an anti-seize plating on them, it can cause problems between the two different anti-seize materials. But on unplated plugs, use anti-seize, absolutely.
The bottom of the plug has to be electrically grounded to head. Too much anti-seize could
compromise electrical contact?
In the 25+ years I’ve been using anti-seize on spark plugs, I’ve NEVER had a problem with it causing grounding issues or mis-fires. And, in the past, I’ve used a lot. Now, I just use a dab on each plug.
If the car came from the factory with anti-seize on the spark plug threads then apply some when replacing them. Perhaps when replacing plugs on the Ford 3-valve engines a bit of nickel-based anti-seize applied sparingly if you must. Otherwise, install them dry.
I had a tech in the shop who insisted, despite my advice, to apply anti-seize to spark plugs. I finally had to throw the anti-seize away.
The biggest issue is leaving plugs in until hxxx freezes over and then facing the aggravation and expense of getting them out and repairing the threads.
Personally, I’ve never seen a problem caused by anti-seize and JMHO here, but torque wrench specs should be taken with a grain of salt. There’s no way on Earth I will crank one down to 15 Ft. Lbs. in an aluminum head.
It should be noted that torque specs can be all over the map. One particular plug spec is given as 7 to 15 Ft. Lbs. and that equates to hand grenade territory. Throw it and you’re bound to hit something.
That’s right up there with the Harley Davidson spec on rocker arm sideplay; .004 to .025. Good thing the A-bomb landed next door… 
Here’s what I do: I put a very tiny amount of moly-lube on the threads, then hand tighten with a 8 inch long ratchet wrench just so they are snug, but not tight. I try to do it to the torque specs, but I do it by feel rather than using a torque wrench. (Here’s how to develop the feel: If you press on a weight scale so it reads 10 pounds, then remember how hard you had to press, then use that same amount of force on the end of a 12 inch wrench, that will give you appx 10 foot pounds of torque.) I try to error on the too-little torque side. I check them again in about a month to see if they need a re-tightening, once in a while they do, but they usually don’t required further tightening. And so far – 200 K miles on this particular car – the spark plugs have come out without any difficulty.
My Lincoln has aluminum heads (4.6 DOHC) and the directions on the package for the plugs used in that motor do not even give a torque spec.
In a nutshell, the directions say to run them down and snug them up.
Same for my daughter’s '05 Mustang 4.0.
With gasketed plugs I run them down and go another quarter turn and with tapered seat plugs it’s run them down and go an 1/8 of a turn more. I’ve never had one come loose yet or strip yet.
I use NGK plugs and have never used antiseize on plugs even when using other brands.
I do, however, believe in torque wrenches. Many of us here have changed hundreds of sparkplugs, in some cases perhaps thousands, over the years. That experience can enable one to estimate the proper torque almost flawlessly. But for someone who’s new to the process it could be difficult to estimate 20 lbs/ft (or whatever).
I actually never used torque wrenches on sparkplugs in the old days, but some years back I began to question my own ability to tell when I was putting 20 pounds on my 12" wrench. I started using torque wrenches and just feel more secure doing so. It takes the guesswork out of it.
I have started using a torque wrench on spark plugs beginning when I got my present vehicle 8 years ago. Before that I tightened them snug and then very slightly more (like I was told in auto repair class). I have been using anti-seize for the past 25 or more years and it never created any problem at all. The plugs always come right out without a fight. I have been using anti-seize and torquing to specs and have not noticed any stripped threads. I use only a very small amount of anti-seize and I don’t want to ride with plugs that are too loose.
Some companies like NGK and even Denso spark-plugs are already coated. The plug manufacturer specifically says NOT to use anti-seize.