Dave :
Don't know if this answers your question, but I've noticed that most, if not
all US cars (running on unleaded gas) now have black tailpipes.
IMO, what happens is that at least once in the car's lifetime, it was rich
enough to smoke, leaving carbon deposits in the tailpipe, and the tailpipe
never gets hot enough to burn off the carbon. Many cars (that pass the
California required smog inspection) seem to blow a little black everytime
they start cold.
Lead oxide, of course, is white (that's why they used to use it in paint),
so I've always assumed that was the white in leaded tailpipes.
I would guess the deposits on your plugs are from your Valvemaster, as my
plugs stay almost perfectly clean (or have black soot) if I don't use an
additive.
Randall
David Hill wrote :
>
> I've been researching on behalf of all of us-in the UK at least.
> I noticed, after changing to unleaded fuel + Valvemaster
> Plus, that the
> tailpipe colour on both my classics is black.
> It used to be that tailpipe colour could be used to gauge mixture, i.e
> white=weak, light grey=right, black=rich. Looking at moderns
> using unleaded,
> they also had black pipes.
> So, I asked Shell-they hadn't tested this aspect and weren't
> prepared to
> comment. Then, I asked BP-their expert was unavailable on
> three occasions.
> So...I asked Castrol. The tech dept. said that the tailpipe
> colour was due
> to lead halides in the exhaust gases and that these are no
> longer present,
> hence no colour. Sounds reasonable to me but, looking at the
> plugs in my
> BGT, they were still whitish-brown at a mixture something
> like right. I'm
> puzzled as to where that colouration comes from.
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