If you are changing your car’s spark plugs, you might wonder if you should grease the threads.
It’s a question thrown around by amateur mechanics, and while it may seem like a neat idea to prevent it from seizing or preventing future removal, it’s best to know what to do.
Today, in this blog post, we’ll discuss spark plug grease on threads, why it’s important, and the best practices when installing spark plugs.
Topic Summary
What Is Spark Plug Grease?
Spark plug grease (sometimes called dielectric grease) is a silicone-based compound used to seal wiring and components against moisture, debris, and corrosion.
It is generally installed on the ceramic end of the spark plug and boot to prevent voltage loss, misfire, and arcing.
Dielectric grease is necessary for the electrical components of the spark plug, but should you grease the threads as well?
Why Do You Put Spark Plug Grease on Threads?
The simple answer is that grease or any other type of lubricant should not touch spark plug threads. It’s an illusion that using grease will ease away future removal, but it can be even worse. Here’s why:
1. Interference with Torque Specifications
It’s imperative to use the proper torque for the right amount of spark plugs to operate and seal. Oil can impede the contact between the plug and cylinder head, causing over or under-tightening.
The result can be an issue with threads in the cylinder head or a problem with a loose spark plug that could cause poor performance or engine damage.
2. Thread Seizing Prevention
Most contemporary spark plugs are usually plated to prevent the plug from seizing. Its coating does not require other lubricants such as grease or anti seize materials.
The coating allows the spark plug to be added and removed without removing the threads or wearing away at them.
3. Grease Can Affect Heat Transfer
Spark plugs must be efficient heat transfer equipment that won’t heat up. Once the threads are greased, it can become an insulator that prevents heat from dissipating properly. That will overheat the spark plug, and it might ruin the engine.
4. Attracting Dirt and Debris
Lubricants draw dirt, leaves, and other pollutants to spark plug threads. These particles can clog the threads and break the head of the cylinder or break the connection between the spark plug and the engine.
What is the Best Grease For Spark Plug Threads?
It is always best not to use grease on the spark plug threads. Today’s spark plugs are usually coated in a tin coating that stops the plug from sizing and doesn’t need extra lubrication.
For spark plugs, if you do not already have lubricated and need to use, use an anti seize compound, not grease.
Anti-seize specifically avoids thread seizing without affecting the torque settings. However, applying anti-seize to pre-coated plugs will halt installation and overtighten it.
The manufacturers typically recommend that you do not use lubricant on spark plug threads unless it is specifically stated for your type of spark plug.
The dielectric grease works best for electrical interfaces such as the ceramic part of the plug and boot.
It will hold moisture and corrosion from the spark plug boots and maintain good electrical conductivity without misfiring.
The Role of Dielectric Grease
You don’t want grease on the threads, but dielectric grease helps install spark plugs. Spraying it across the ceramic side of the plug and the spark plug boot can:
- Let water not seep in and corrosion the electrical connection.
- Allow the spark plug wire to come off without damaging the boot.
- Guard against misfires from electrical arcing.
Dielectric grease provides an insulating barrier, not electrical conductivity, so the spark stays pointed correctly to start the air fuel mixture in the engine.
When To Use Anti-Seize on Spark Plugs?
Spark plug grease isn’t to be put into the threads, but an anti seize compound is sometimes used. But the good news is that most current spark plugs have a built-in plating that eliminates anti seize.
You can also add a thin layer of anti seize to your spark plugs, but only very lightly. If you do end up using anti seize on non coated spark plugs, follow these instructions:
- Apply a little, but don’t use too much.
- Use only in the middle portion of the threads, preferably not the first two threads at the electrode.
- Ensure you calibrate the torque when installing the plug because anti seize diminishes friction and can cause over tightening.
FAQs on Spark Plug Grease on Threads
Should I Apply Grease To Spark Plug Threads?
Oh no, you shouldn’t grease the spark plug threads. The grease hinders the correct torque, wears threads, makes the heater heat up, and pulls dirt, leading to engine problems.
What is Dielectric Grease Used for in Spark Plug Installation?
The ceramic surface of the spark plug and the boot are coated with dielectric grease to prevent moisture, corrosion, and electrical overheating. This keeps the electrical line tight and prevents misfires.
Do Modern Spark Plugs Need an Anti Seize Compound?
Today’s spark plugs are typically plated to resist seizing, so an anti-seize compound is unnecessary. Always read the label on all anti-seize compounds before use.
Can Using Grease on Spark Plug Threads Damage My Engine?
Yes, grease on the threads will over tighten or under tighten the thread and cause you to torque them incorrectly. This can destroy the threads on the cylinder head or make the engine run rough.
Is It Necessary To Use Dielectric Grease When Installing Spark Plugs?
This is optional, but the ceramic block and boot need dielectric grease. It prevents the electric connection from moisture corrosion, and it is convenient to remove the spark plug wires easily later.
Conclusion
Rubbing grease or lubricant into the contacts of a spark plug makes sense, but this does more harm than good.
Modern spark plugs are usually coated so that no additional greases or anti seize agents are required. Instead, concentrate on applying dielectric grease to the ceramic portion of the spark plug and in the boot for a reliable electrical connection and corrosion resistance.
Consult your vehicle’s service manual for details on maintaining and replacing spark plugs. Manufacturer recommendations will ensure your car’s engine runs at peak performance and is as long-lasting as possible.