The spark plug anti seize debate isn’t new. Some mechanics have always used it when installing spark plugs, while others swear against it.
In this article, we’ll answer those questions and more, including why some recommend applying anti-seize to spark plugs and some common spark plug anti-seize questions and answers.
This Article Contains:
- Should You Put Anti-Seize On Spark Plugs?
- Why Put Anti-Seize On Spark Plugs?
- How To Use Spark Plug Anti-Seize Safely
- 4 Spark Plug Anti Seize FAQs
Let’s get started.
Should You Put Anti-Seize On Spark Plugs?
Just about every spark plug manufacturer will recommend against putting any lubrication on spark plugs. NGK spark plugs, AC Delco, Champion, Bosch, Denso, and more all say to avoid it.
The primary reason for this is that almost all modern spark plugs ship with trivalent plating or other types of antiseize compounds already applied.
Adding extra lubrication reduces the torque value, increasing the risk of spark plug thread breakage and metal shell stretch.
If the spark plug thread breaks, it can mean removing the cylinder head for repair. Metal shell stretch changes the heat rating of the spark plug and may damage the engine through pre-ignition. It can also create heat transfer and electrical conductivity issues.
In almost all cases, adding lubricant is unnecessary and can be detrimental.
Why Put Anti-Seize On Spark Plugs?
Since anti seize is a form of lube, the main benefit of applying it to your spark plugs is to make replacing them in an aluminum head far easier.
Changing spark plugs several decades ago was more of a hassle than today. The plugs would fuse to the cylinder head through galvanic corrosion, making spark plug removal a particularly unpleasant job.
Often mechanics applied copper grease or an aluminum or copper anti seize to prevent galling and galvanic corrosion and improve corrosion resistance.
However, today, almost every major automotive spark plug manufacturer applies zinc or nickel plating to improve corrosion resistance and protect against galling. The metal plating effectively removes the need for spark plug grease.
On another note, an antiseize compound isn’t as crucial on plugs installed onto cast iron heads compared to an aluminum cylinder head.
So, let’s see how you should use it.
How To Use Spark Plug Anti Seize Safely
Although it’s generally recommended to avoid using anti seize on your spark plugs, there is a safe way to go about it if you’d like to go ahead anyway.
Though before beginning, it’s crucial to point out two things:
1. Anti Seize Reduces The Friction Coefficient
This means you need to decrease the dry torque value by about 20%. If you’re unsure, unless it specifically states “wet torque,” you can assume its dry torque values. Wet torque simply means that the spark plug threads are lubricated.
It’s important to point this out because if you frequently tighten a wet plug thread to dry torque values, you’ll eventually break the spark plug head.
When tightening the plug, reduce the torque spec on the spark plug by about 20% when applying plugs with anti seize. In general, the proper torque spec for spark plugs is between 3.9 to 4.5 PSI. This applies to all spark plugs, including copper, platinum, and iridium plugs.
Iridium plugs offer the most durability, while copper provides better performance.
An under-torqued spark plug can cause excessive vibration and irregular heat dissipation. Inadequate heat dissipation can cause damage to the spark plugs and engine block.
Furthermore, keep in mind that it’s much easier to overtighten the spark plug when anti seize lubricant is applied. Over-torquing the plugs will damage them, which can lead to engine damage.
2. You Need A Tiny Amount Of Anti Seize
In addition to needing just a dab, you should only apply it to the middle portion of the threads, leaving the first plug thread free of anti-seize.
The first thread is closest to the spark plug ground and electrode. You don’t want anti-seize on this as it can cause the spark plug to short, resulting in engine misfire, spark plug thread damage, combustion gas leaks, and more.
If going ahead, a nickel-based anti seize compound is generally better since it has the highest heat resistance.
And remember: Never use anti-seize on rubber seals, engine internals, or any bolt (such as cylinder head bolts) or lug nut that requires a thread compound. Thread compound like Loctite or Permatex is adhesive, while anti-seize functions similarly to grease.
Let’s find out a bit more about spark plugs and anti-seize.
4 Spark Plug Anti Seize FAQs
Let’s take a closer look at some common spark plug anti-seize questions and their answers:
1. Why Do Torque Values Change When Anti-Seize Is Applied?
Friction is the reason.
Since the anti seize compound functions as a lubricant, there is much less friction between the two materials, and more force can be applied to the spark plug preload.
Preload refers to the tension between the spark plug and the cylinder head that provides the friction holding the plug in place. Applying too much torque can strip the spark plug.
2. Can You Use Dielectric Grease On Spark Plugs?
Dielectric grease is commonly used to seal the connection between the spark plugs and the spark plug wire. Since dielectric grease doesn’t conduct electricity, you shouldn’t apply it to spark plug wire metals or the pins and sockets of any electrical connection.
3. How Do You Know If You’ve Overtightened A Spark Plug?
When installing a new spark plug, it’s best to forego a torque wrench and begin by hand tightening the plug. This way, you minimize the risk of cross-threading.
You’ll also get a better feel when the plug is in the correct position. You can always use a torque wrench for another half-turn or so if necessary. When you feel the plug tighten slightly — that’s your cue.
If you’re worried you’ve stripped the plug, you’ll know if the plug keeps turning without tightening or, more seriously, the plug won’t spin out. If the threads are stripped, the best solution is a Helicoil.
Alternatively, you could replace the cylinder head, but this is considerably more expensive.
4. What’s The Best Solution To My Spark Plug Issues?
If you’ve replaced the spark plugs but mistakenly damaged them, you might be thinking, ‘maybe it’s best to let a professional handle this.’
In this case, why not contact RepairSmith?
RepairSmith is a mobile auto repair and maintenance solution offering:
- Competitive and upfront pricing
- A 12 month | 12,000-mile warranty on all repairs
- ASE-certified mechanics
- Easy and convenient online bookings
- Only high-quality equipment and gear when carrying out repairs and maintenance
Generally, putting an antiseize compound on spark plugs isn’t recommended as they already ship with an anti seize coating. However, if you’re seasoned at vehicle DIY, make sure to adjust the torque values if you apply a small amount of anti seize.
If you need help with spark plug removal or need a spark plug replacement, contact the professional mechanics at RepairSmith to handle it.