This pretty much agrees with conventional wisdom out here in Oklahoma
(where we don't bother to marry our cars -- we just shack up with
them). Sump oil temp above 200 is desirable, with preferred range
around 220-230 for small engines. The reasoning is that colder temps
don't fully dissipate the entrained acids and other blowby compounds
that wind up in the oil, and these compounds are damaging to the
engine. It's true that conventional oil deteriorates at these temps,
but that's why you change oil regularly. The newer synthetics and
blends are much more temp-tolerant and can run hotter with less
deterioration.
Oil coolers make sense if you are running hotter than this with
conventional oil, esp. in the summer. This problem might show up as
low pressure after a long summer drive, with the viscosity of the
conventional oil not able to hold up to prolonged high temp running.
Some folks use an oil cooler, but screen it off in the winter to keep
the oil from running too cold when the weather is cool. Also
available are oil cooler thermoststs that only send oil to the cooler
matrix when it's above a preset temp (about 180 or so -- this is
sensed outside the sump, where it has already cooled down some from
the sump temp). With the new synthetic oils I don't think an oil
cooler is such an issue unless you are running VERY hot, and then you
probably have other problems anyway.
I've had excellent luck with the Quaker State blended synthetics in
all my older vehicles. QS's lubrication engineers steered me away
from their pure synthetic in any car older than 1980, unless I was
changing all seals on an engine rebuild (same for tranny and axle).
But they said their semi-synthetic blend could be run with no seal
problems, and it is very temperature tolerant. As far as rebuild
theory, I like to run the first 500-1000 miles on a good conventional
like Valvoline (it's known for its detergent action), then switch to a
semi-synthetic blend thereafter.
MD
---Bkitterer@aol.com wrote:
>
> For what it is worth,
>
> From "The RV Handbook", 2nd Edition by Bill Estes, 1998(?)
>
> "Oil temperatures in RV engines usually run 250F to 270F during
sumertime
> driving and may exceed 300F on grades in hot weather. . . . Engine
> manufacturers say that temperatures up to 285F are within their design
> parameteres."
>
> Bob and Annice
> 1960 Sprite (Mk IV in disguise)
>
==
Michael B. Dietsche, P.E.
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