Anti-seize compound on spark plugs is a topic of genuine debate among mechanics. Some swear by it; others say never use it. Here's the practical truth backed by engineering data.
What Anti-Seize Does
Anti-seize is a metallic paste that prevents galling and corrosion between threaded fasteners exposed to heat cycles. It makes future removal much easier, especially on fasteners that go into aluminum — which is highly susceptible to seizing threads with steel fasteners over time.
The Problem: Anti-Seize Reduces Friction
Torque specifications are calibrated assuming a certain amount of thread friction. Anti-seize reduces that friction by 20–25%. If you apply anti-seize and then torque to the dry spec, you're effectively overtightening by 20–25% — which can stretch or break spark plug shells, or worse, pull aluminum threads.
The Solution: Reduce Torque by 20–25%
If you choose to use anti-seize: apply a thin coat to the plug threads (not the first two threads, to prevent combustion contamination), and torque to approximately 75–80% of the dry spec. For example, if the spec is 20 ft-lbs dry, torque to 15–16 ft-lbs with anti-seize.
NGK and Champion's Stance
Both NGK and Champion state that their plugs do not require anti-seize — their plating provides adequate protection against seizing in most applications. Anti-seize is most beneficial when plugs will be in service for very long intervals (60,000+ miles) in aluminum heads.
Shop spark plugs and Permatex anti-seize at Texan Supply with free shipping.