Rick's Free Auto Repair Advice

Red spark plug electrode and insulator

Red spark plug electrode and insulator

What causes a Red spark plug electrode and insulator?

red tipped spark plugs

red tipped spark plugs

The most common cause of a red spark plug electrode and insulator is the use of an octane booster containing Methylcyclopentadienylmanganesetricarbonyl (MMT) in the fuel or iron oxide particles present in the fuel system.

Octane booster causes red spark plug electrode and insulator discoloration

If a fuel additive contains an iron component, it can red spark plugcause red deposits on the insulator nose, center electrode, and side electrode. The iron coating is electrically conductive and can cause misfiring.

Source: Bosch

The iron coating is Ferrocene; “an organometallic compound with the formula Fe(C 5H 5) 2. The molecule is a complex consisting of two cyclopentadienyl rings bound to a central iron atom. It is an orange solid with a camphor-like odor, that sublimes above room temperature, and is soluble in most organic solvents.”

MMT is also used in octane boosting gasoline additives. Using more octane booster than necessary will usually make the plug look a wet red brick color.

Iron oxides from fuel system corrosion is also a cause of a red spark plug electrode

Source: Underhood Service

The fuel filter and fuel pump sock will prevent solid rust particles from entering the combustion chamber, but they can’t prevent soluble iron oxide from entering the combustion chamber. During combustion, the iron oxides deposit on the spark plug insulator, center and side electrodes.

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