Ed--ran across similar info years ago.
It seems the presence of Sulphur in the oil and gasoline raised the dew
point temperature in the crankcase and increased condensation which caused
the formation of more and more sulphuric acid in the oil, leading to
increased wear.
Probably less of a concern with reduced Sulphur in oil/gas these days, but
still a good reason to change oil in your daily driver at reasonable
intervals no matter how much particulate matter the filter takes out.
Lance
----- Original Message -----
From: "The Weldons" <2weldons@earthlink.net>
Ed Weldon wrote......
> Running too cool--
>
Besides the obvious
> problems of ring sealing and friction from higher oil viscosity there is
the
> phenomena of increased ring wear due to the presence of minute amounts of
> liquid acid sulphates in the ring to cylinder wearing interface. Some 30
> years ago I was poking around in the university library when I should have
> been studying and found an late 1930's SAE paper on this subject. Seems
the
> authors mixed some radioactive tracer into a batch of cast iron they used
to
> make piston rings and then ran wear tests at various engine conditions and
> cooling jacket temperatures. (Imagine trying to do that kind of project
> today!!). Bottom line was that the wear rate was worst at the lowest
> temperatures (80-100F) and decreased to a negligible amount at around
> 160-170F. They concluded that wear was caused by the presence of water
from
> combustion byproducts combining with sulphur to form sulphuric acid which
> accelerated wear as long as it was cool enough to remain in liquid form.
Wish
> today I could find a copy of the original paper.........Ed Weldon
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