Quite apart from lead in fuel or not being a completely different issue to
ZDDP in oil, your one-off uncontrolled experience is completely at odds with
the tests that the Motor Industry Research Association performed on behalf
of the Federation of British Historic Vehicle Clubs when lead was about to
be removed from petrol in the UK. These tests used multiple, new, BL (known
to be more susceptible to valve seat recession than other manufacturers)
engines run for many hours at high rpm and loading, and showed conclusively
that significant recession did occur. They tested a number of additives on
behalf of their manufacturers which gave a wide range of results, only four
of which gave a significant reduction in recession, although none were as
good as lead. They publicised these four products, and subsequently a
fifth, but not the ones that failed. For some years several petrol
manufacturers produced a grade called Lead Replacement that contained one of
these additives, including Shell.
Subsequently a quote attributed to BMW said that an engine that has run 30k
on leaded, and not had replacement valves or seats recut, will have enough
lead leached into the valves and seats to protect them 'for the rest of
their normal service life'. Even though my roadster engine falls into that
category, and because I run it quite often for long durations at motorway
speeds, I choose to use one of the additives. One bottle a year at about #6
is cheap insurance.
And maybe replacement cams and tappets *are* softer now than the originals,
but doesn't that *make* the case for using an oil with higher levels of ZDDP
if ZDDP really does reduce wear as is incontrovertibly the case? Again, one
chooses to or not, but it is better to be informed than uninformed.
PaulH.
----- Original Message -----
> Shell used my restored Austin Healey BJ8 with rebuilt engine to test wear
> using their lead free fuel. They made a special measuring device and took
> enormous care to measure the wear due to my driving (reasonably hard but
> not auto-cross ertc) the car for a year. Result - no measurable wear !
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