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Re: Black spark plugs mean what?
Yes it is my understanding that burnt is too lean, and black and oily is to
rich, and golden brown is just right.
General rule: A flat (matte, "sooty") black indicates running rich;
shiny ("oily") is typically burning oil ("oil fouling" -- bad rings,
bad valve guides); tan/golden brown is just right, white (assuming
you've got some miles on them!) is lean, and melted is way too lean.
"Mild" rich/lean (black/white) might just be too cold/hot of a heat-
range for your particular driving conditions (e.g., if your car idles
all day long, you might want a one step "hotter" plug, while if you
spend all day "on the track" (you know, averaging 108.9 mph, etc.)
you might need a step colder plug from factory-speced nominal plug.
Back when I autocrossed my Lotus, I learned to carry "track" (cold)
plugs for the autocross, and "normal" (factory-spec) plugs to drive
to and from the events...in retrospect, I'm amazed I never managed
to strip any of the threads in my, er, youthful exuberance.
>sorry for the basic nature of this mail, but what do black spark plugs
>mean? I think it means that it is running too rich, is that right?
>Which would make sense cause i am getting very poor gas mileage.