CC:

So, you’re replacing a set of spark plugs, and you’ve heard different opinions about using anti-seize on the threads. One technician says yes, and one technician says no. They’re actually both right, but knowing when to use it, and what kind to use is what you need to know.

Let’s look back at technology from a time when cast iron cylinder heads were on just about everything. Back then, black oxide was the most common coating on spark plugs, and we really didn’t see an issue with seized plugs. To start with, steel, which the spark plug shells are made of, and cast iron didn’t experience galvanic corrosion like steel and aluminum.

The black oxide coating offered additional corrosion resistance for any that may occur, and also the fact that plugs were replaced much more often just didn’t give corrosion a chance to get a grip. That all changed with aluminum cylinder heads and extended spark plug service intervals, and anti-seize became necessary to prevent the problem.

Luckily, spark plug technology quickly adapted with a nickel coating on most modern plugs that prevents corrosion with aluminum and for the most part eliminates the need for anti-seize, however there are still times to use it.

The absolute best rule is to only use it when it is called out specifically by a manufacturer, because don’t forget that not only will any type of lubricant affect torque, but it can also affect heat transfer and electrical conductivity.

Now, you can make the decision to use it, and a good example is black oxide plugs in cast iron heads. Normally you wouldn’t use anti-seize, but what if it’s a plow truck that will see four or five months out of the year wallowing in salt brine from the roads? Believe me you’re going to want to use it. In this case, copper anti-seize, which is a copper/graphite blend, would be the correct type because it withstands high temperatures and provides better electrical conductivity than other blends.

A good example of a manufacturer recommendation is while replacing the plugs on some 04-08 Ford 5.4 liter 3-valve engines that had problems with broken spark plugs. They specifically call for nickel anti-seize, which is a blend of nickel and graphite, has the highest temperature rating and is recommended where copper contamination could be a problem. However, they don’t call for it on the threads, they only specify to apply it to the lower shell, on which carbon build up is the main cause of the problem.

To wrap things up, always use a high-quality plug that is specific to the application, always follow manufacturer instructions regarding anti-seize, and if you do use it, be sure to use the proper blend. Thanks for watching, we’ll see you next time.

This video is sponsored by Autolite.