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Should Spark Plugs be Installed with Anti-Seize Compound?

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    Should Spark Plugs be Installed with Anti-Seize Compound?

    A friend of mine who has a lot more money than me is interested in buying an Ultimate Driving Machine. Since he knows little about cars (other than he knows what he likes), he asked me to do some research for him on a BMW website. While there, I came across a forum discussion on the choice and installation of spark plugs. One member insisted that anti-seize should never be applied to spark plug threads and as evidence quoted the following information taken from Autolite and AC/Delco:
    Autolite
    We do not recommend the use of any anti seize products for installing spark plugs. Anti-seize compounds are typically composed of metallic, electrically conductive ingredients. If anti seize compounds come in contact with the core nose of the plugs, it can lead to a misfire condition. Anti seize compounds can also have a torque multiplying effect when installing plugs. This can lead to thread distortion and thread galling resulting in cylinder head damage. Autolite spark plugs are nickel plated to resist the effects of corrosion and seizing. However, plug seizure is aggravated further when steel plugs are installed into aluminum cylinder heads for a long period of time.

    AC/Delco
    Do not use any type of anti-seize compound on spark plug threads. Doing this will decrease the amount of friction between the threads. The result of the lowered friction is that when the spark plug is torqued to the proper specification, the spark plug is turned too far into the cylinder head. This increases the likelihood of pulling or stripping the threads in the cylinder head. Over-tightening of a spark plug can cause stretching of the spark plug shell and could allow blowby to pass through the gasket seal between the shell and insulator. Over-tightening also results in extremely difficult removal.

    Champion
    The following material is excerpted from the Champion Spark Plug Handbook. It can be accessed at:


    Champion spark plug shells (the threaded part) use an extruded steel to maintain exact tolerances. The extruded shell goes through a cold rolling process to form the threads. This prevents sharp edges which could cut new threads into aluminum cylinder heads. Once the shell is formed and threaded, it is zinc-plated to extend its life and reduce the chances of seizure in aluminum cylinder heads. Our latest technology combines Tin Tac" and ULTRASEAL'M coatings over the plating to further reduce corrosion and seizure. Champion recommends that you do not use an anti-seize compound, since one has already been applied to the plugs at the factory.

    Intrigued, I went a-googling for any information I could find from NGK on this topic. I found this excellent Canadian website that lists the complete set of NGK Technical Bulletins. Go to:


    Or, you can go directly here for NGK's take on the use of anti-seize compound, NGK Technical Bulletin #NGKSP-0907-1:


    According to the Bulletin, NGK states that all their plugs are manufactured with a special metal shell (trivalent) plating to prevent damage to the cylinder head. For plugs with this special metal plating, anti-seize is not recommended during installation. Applying anti-seize to these plugs will cause the installer to mistakenly over-torque the plug in the cylinder head stretching the metal between the last thread and the seal between the cylinder head and plug. This increases the probability that the spark plug will either break during installation or upon removal.

    For plugs without a special metal shell plating, NGK advises the use of anti-seize and provides photos of unplated plugs installed without anti-seize where the steel threads have bonded with the aluminum in the cylinder head requiring replacement or repair of the head.

    Denso also warns against the use of anti-seize in their Spark Plug Installation instructions:
    DENSO spark plugs use iridium alloy for their center electrode. Because of its extremely narrow diameter of just 0.4 mm, engine output and acceleration response are greatly improved.


    Specifically, they state: "If a thread lubricant such as grease is coated on the thread, tightening to the recommended torque is tightening too much; this has been linked to seal leakage. Do not use a thread lubricant."

    Recommendations
    One could simply stop using anti-seize and torque to the factory recommended specs when using shiny metal shell plated plugs as per the manufacturers recommendations, and be done with it.

    Thinking it was the right thing to do, I've always used anti-seize, always used a torque wrench, and tightened the plugs to the middle of the range of the FSM recommended specs (11-16 ft/lbs; 15-22 Nm) for my car. Maybe this is a holdover from the days when plug threads were typically unplated (black) and driven into aluminum heads where damage would have occurred without a lubricant?

    In the future, if I continue to use anti-seize I'll make sure its the lightest possible coating and torque the plugs to the lower end of the range (11 ft/lbs; 15 Nm) to guard against the possibility of over-tightening. One problem with the use of my torque wrench (5-85 ft/lbs; 3/8" drive) is that at the lower end of its range it tends to be outside its area of greatest accuracy and thus makes it difficult to know exactly how close I am to spec. In the interest of greater accuracy it might be better to use an inch/lb torque wrench (1/4" drive?) or to buy a Snap-on; the latter choice would be about as likely for me to afford as it would be for me to afford a new BMW.

    What should you do? As always, I report, you decide.

    Happy Motoring!
    Last edited by goldstar; 02-04-2011, 07:01 AM.
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    #2
    i always use antiseize on spark plugs. no matter the brand . sure save ya alot of headaches...

    Comment


      #3
      Between the conduction issues, heat transfer interference issues, and never once having any issues not using it, I never use antisieze or grease on my sparkplugs. Thanks for posting that, I think I'll stick with my routine.
      '90 AWD Protege, full GTR drivetrain swap, ~320 whp daily driver, RIP, and
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      Comment


        #4
        For an ultimate driving machine where tolerances may be pushed to achieve SUPERnatural performance, anti-seaze compound may be needed. In those specific case it should be used with the same precision you'd use when torguing the plugs down.

        For most of our common needs, it's not necessary. If we pay special attention to make sure we don't ever have fouled or dirt jammed threads, a torque wrench will be all we need. For many years, all mechanics had was experience and a heightened sensitivity for the work. "Mechanics feel" can get you a whole lifetime of accomplished work but you have to have a "sense" for what you are doing.

        Myself, I stick with the torque wrench and manufacturer specs. You really can't go wrong.
        Last edited by 1st Gen; 01-23-2011, 07:41 PM.
        1991 Protege LX with GTX swap, DD
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        Comment


          #5
          Personally, I've never gone out of my way to put anti-seize on the plugs when I change them. I have purchased plugs before with it already on there and never had a problem, and even when I don't use it I don't have a problem removing the plugs when they need replacing. Best bet, follow the manufacturer's recommendations. Being that your friend is buying a German car, I'd follow their directions to the T. They tend to be picky beasts. If there's no mention of it, he should be fine without. Some of the Range Rovers I've serviced have BMW engines, and I've never put anti-seize on the plugs; no issues have ever cropped up because of it.
          1995 626: daily beater, mostly stock. Future NASA racer?

          Next up: Speed6 or RX-8

          Comment


            #6
            Originally posted by goldstar View Post
            Thinking it was the right thing to do, I've always used anti-seize, always used a torque wrench, and tightened the plugs to the middle of the range of the FSM recommended specs (11-16 ft/lbs; 15-22 Nm) for my car. Maybe this is a holdover from the days when plug threads were typically unplated (black) and driven into aluminum heads where damage would have occurred without a lubricant?

            In the future, if I continue to use anti-seize I'll make sure its the lightest possible coating and torque the plugs to the lower end of the range (11 ft/lbs; 15 Nm) to guard against the possibility of over-tightening. One problem with the use of my torque wrench (5-85 ft/lbs; 3/8" drive) is that at the lower end of its range it tends to be outside its area of greatest accuracy and thus makes it difficult to know exactly how close I am to spec. In the interest of greater accuracy it might be better to use an inch/lb torque wrench (1/4" drive?) or to buy a Snap-on; the latter choice would be about as likely as it would be for me to be able to afford a new BMW.

            What should you do? As always, I report, you decide.

            Happy Motoring!
            Since my profession is working on cars, I have come across a lot of plugs that have been corroded and hard to remove, Which I mostly attributed to people thinking they are only tight if you cant turn them anymore, and a little bit to an engine that was eating water and rusting the threads that are exposed in the combustion chamber and into the head a little. I have used a light coat of antisieze on plugs many times and I use the "mechanics feel" on it to tighten them up, with no ill effects.

            Goldstar I have a nice Snap-on 3/8 digital torque wrench that does inch/lbs, ft/lbs, and Nm with the push of a button that I bought about 6 years ago and I love it, but at the time I think it was about $280 or more I paid for it. It has served me well but I need to get it and my other Snap-on 1/2" analog calibrated after this long and the use it gets.
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            Comment


              #7
              I might use it on a 3v ford v8, but nothing else. As long as you use good spark pluges (ngk) you should never have a problem.
              sigpic

              Comment


                #8
                I agree with many others when I say, I replace sparkplugs for a living... ok I dont do them day in and day out but I do replace them on cars that have 30k miles - 300k miles... I have yet to remove a plug with anti seize on it and I have yet to see a any damaged threads. Considering the milage and lack of damage on the dozens and dozens of vehicles I have replaced sparkplugs on, that and the suggestion by ALL manufactures listed to stay away, ill continue not using antiseize.
                There are no stupid questions, just stupid people.

                Comment


                  #9
                  who torques spark plugs?

                  I change them so frequently I never seem to need anti-seize.
                  sigpic

                  03 Accord DX: K24/5MT, peasant-spec old man's car
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