Crud Build-up on the Plugs.

[I66coupe]

Pulled the plugs in the old 200 today to give them a look. Car not running great lately. This is what I find. Crud buildup on #3-#6. #1 and #2 looked clean with a reddish brown coating.

Any ideas what is happening? I figured if it was oil burning, it would be dark brown or black. This residue is reddish brown.

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[JackFish]

Referring to the Chilton's, that looks like MMT fouling.
Methycyclopentadienyl Manganese Tricarbonyl.
Anti-knock additive used to replace lead apparently.

No engine malfunction is indicated and the deposit will not affect plug performance any more than lead...

Clean, gap and reinstall they say.

 

[I66coupe]

Thanks JF, thats what I was thinking it was. I do use a lead substitute. I did clean, gap, re-install.

I guess I will be inspecting them on a more frequent basis.

 

[addo]

Had the same freakout here. MMT it is; I contacted the additive makers and they confirmed it.

 

[I66coupe]

Probably time to install hardened seats and be done with the additive.

 

[GrantD]

Thats what mine looked like except maybe a little lighter, and mine was just from the pump gas. Swapped them today and it runs a lot better. I have 1980 motor though.