Let’s settle the debate! Anti-seize or no anti-seize on spark plug threads?

Well, what is anti-seize?  Anti-seize compound is commonly applied to fasteners to prevent the threads from becoming galled or damaged, especially when dissimilar metals are involved. For people that live in locations where corrosion is a persistent issue, anti-seize is an invaluable tool to have, helping to prevent thread damage and contamination from corrosion. 

So, apply to spark plug threads? No! Why not? By doing so, you actually reduce torque values by 25% to 30%!

This is commonly forgotten and extremely important. Torque ratings on fasteners are based on their target clamping force. Anti-seize will act as a lubricant; those lubricating properties will significantly decrease the required torque to achieve the desired clamping force. This is often referred to as a torque multiplier. Using anti-seize without reducing the required torque value can strip the threads or stretch the bolt in extreme situations and cause over tightening of the spark plug and possibly even breakage of the plug.

Over tightening can also distort the spark plug shell, causing a leak which would allow blow by to pass through the gasket seal between the shell and insulator. 

Anti-seize can also affect the grounding ability of the spark plug in todays higher voltage ignition systems. 

Virtually all spark plugs now feature a special anti-seizure nickel or zinc-chromate shell plating. Basically, you can think of the plating as a replacement of thread compound or copper slip.

Most spark plug manufacturers do not recommend the use of it when installing new plugs. Most automobile manufacturers have no mention of applying it to spark plugs when replacing the plugs. 

Final recommendation: clean the threads of the head and install dry.

This video is sponsored by Autolite.