> i may be way off base here and IM sure you all will tell me if i am.
> back in the old country of leaded gas it was customary after a long run to
> check the color of the inside of the exhaust pipe. if it was a nice
> light brown
> you knew it was running right. now i never see that any more and i recall
> reading that unleaded does not give that indicator.
> if all I have said is true would it not also apply to the old spark plug
> color guides too?
It does apply to tailpipes, I believe ... and the plug colors probably do change
a bit. But IMO the effect of unleaded is much less at the plug.
Basically the tailpipe never did get hot enough to burn away any carbon soot, it
was just coated over by the white lead oxide (so white it used to be used for
paint pigment) in the exhaust. But the plugs get plenty hot enough to burn away
the soot, and a proper running plug had little or no lead deposits on it anyway.
So the plug colors remain pretty much the same, except that you never see lead
fouling any more.
Randall
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