Allan, et al. unwashed,
Back in mid-May, I saw something on Speed Vision that piqued my curiosity.
It was a reference to the Mobil 1 "fiasco" and had to do with using it in a
turbo-charged airplane. Well, like all of us motor-heads, I was naturally
curious about what this was all about. I posted a question to this list,
but didn't get much response. I did, however, find a ton of stuff by
searching the Web; more than you'll ever want to know, in fact. One of the
many places I visited was the Red Line Web site; www.redlineoil.com. You
can also get information on their Water Wetter, and other products, if
you're interested. But getting back to the subject, you may have noticed
that for some time now car manufacturers have been recommending single
weight motor oil. Now, frankly, this really goes against my grain. For
years I've had this idea that the best motor oils are multi-grade and the
more multi, the better. Hey, 5W-50 is music to my ears!! Turns out we've
been wrong; in fact the whole industry has been wrong for most applications
(except maybePruhoe Bay and places like that ). Wear tests show that just
straight 30W produces less wear than comparable multigrades. The
multi-grades break down quicker, especially in high shear-rate conditions
such as on the rod bearings and the cam. The breakdown has to do with the
long chain polymeric thickeners that are added to a straight weight oil
base. These polymers are only stable up to about 210 F where they start to
break apart and/or are torn apart because of high shear stresses. This
produces nasty stuff you don't want in your engine, causing wear and slug
deposits. If you change oil frequently and keep it below about 210 F, then
maybe mulit-grades are OK. Now, mind you, this is just a very abbreviated
explanation. If you want to research the subject, you can do a Web search
and write a thesis. Now synthetics opens up another level of complexity.
The main problem with synthetics seems to be that they are very powerful
solvents and they get past seals, gaskets, etc. I have definitely had this
problem myself. Just try keeping synthetic oil in you tranny or
differential. It's almost impossible to keep it from leaking at least a
little bit. The synthetic oil manufacturers claim this problem has been
reduced, but I don't know how or how much. But every credible source I have
read claims much reduced wear with synthetic oil. And furthermore, Mobil 1
is just about as good as they get; right up there with Red Line, etc.
Now, like almost everybody, I'm very particular about the oil I put in my
car; especially in the engine. I started with synthetics in the tranny -
big improvement - then in the diff - and finally now that's all I use in
the engine. Actually, I started with Aeroshell which is 50/50 natural and
synthetic. But so far, I haven't been able to break the multi-grade habit.
Been using Castrol Syntec 5W-50 ever since I rebuilt the current motor and
it seems to do a great job. Maybe I need to join Multigrades Anonymous.
Then, when it's time to change oil, I just have one of you guys come over
with a case of straight weight oil and provide moral support while I put it
in my motor. You know, the mind may be strong but the flesh is weak!!
One other quick thing. Racing oils are low-detergent/low-ash. The low ash
helps prevent pre-detonation. Of course, low-detergent is not a good idea
for the long haul. So I wouldn't recommend using any oil that advertises
itself a "racing" type. Not unless you really are racing, of course. And
then, probably only if you have a pretty high compression ratio, a blower,
or nitrous oxide injection. I don't think that's you or me, Allan.
If you want to know more, hit the Web. But thanks for the interest.
Best regards,
Bob
At 09:09 PM 8/24/98 -0700, Allan Connell wrote:
>Bob,
>
>To those unwashed, illiterate beings such as myself, would you be so kind as
>to expand somewhat on the "current industry thinking....that multi-grades
>(oil) are bad" ?
>
>Appreciate the help. You expand (or, is that: expound,) so well anyway. :)
>
>I am curious but not yellow in San Diego.....
>
>Allan
>B9472373
>
Robert L. Palmer
Dept. of AMES, Univ. of Calif., San Diego
rpalmer@ames.ucsd.edu
rpalmer@cts.com
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