Re: oils, by Nelson Quimby "The Wing Doctor"
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From "NQ" <elso@chi.tds.net>
Organization Elso Graphics
Date Sat, 17 May 1997 23:00:22 -0400
Newsgroups fj.rec.motorcycles
Message-ID <01bc6337.a06bc620$270df6cc@elso>
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One of the most frequent questions I'm asked is "what's
so different about oils and what should I use?" When people have
a question they seem to get as many opinions as they can, which
in the case of oil, only adds to confusion, because there are so
many opinions. Well, I want to give you some of the facts about oil.
One statement I hear quite often is "oil is oil is oil,
it all comes from the same place and is packaged by somebody else".
For the most part this statement is absolutely correct, since a lot
of the finest brands of oil started out as Pennsylvania crude oil,
(Pennsylvania crude being one of the best). What makes one crude
oil better than another, you ask? The better crude thins the least
as it's temperature rises, but that's not real important right now.
What is important is, "motorcycle oil vs automobile oil". The
differences are the additives that are used, both in quantity
and quality. The oil you put in you car is perhaps 10 to 20%
additives. Yet a specially blended motorcycle oil can be 50%
additives. One of the more apparent (cushions things like
transmission gears) additives found in both types are polymers,
(multi-viscosity additives). We all know that oil has a tendency
to thin out as it gets hot, this is where these polymers come into
play. Probably best described as thin (microscopic) strands of
plastic. Have you ever heated a piece of plastic and watched the
results, well if not, the plastic curls. And that is kind of what
happens to these polymers, they expand and curl causing the oil to
actually thicken as it warms up to counteract the thinning of the
crude base.
Now polystyrene-type polymers found in most automobile
oils don't have a lot of strength and will be 50% sheared, or worn
out, after only 2000 miles in a car engine. So you can imagine what
kind of shape they would be in if they where exposed to hundreds or
thousands of pounds pressure between transmission gear teeth. With
that, the polymers in motorcycle oil must be shear resistant and
can cost 10 times more than those used in automotive oils. This
brings me to another very important additive, extreme-pressure
additives.
Theory of lubrication is to maintain a film of lubricant
between two surfaces thus preventing metal-to-metal contact and
metallic friction. Though the polymers help in this area polymers
alone can't survive all of the squeezing and shock loads of a
transmission and camshaft lobes. So that's where the additive
"ZDDP" or "Zinc Dialkyl Dithiophosphate" comes in to play,
(Can you say Zinc Dialkyl Dithiophosphate?) Don't feel bad,
I had a tough time with this one. I don't even pretend to be a
chemist. But I do know that zinc, being a mineral, clings to the
metal surfaces so when all else fails the zinc will protect the
surfaces from direct metal-to-metal contact. Now the phosphorous,
an essential element in ZDDP, is limited by law in oils marketed
for automobiles because the catalyst won't survive when confronted
with the phosphorous. But since motorcycles don't have catalytic
converters larger quantities of ZDDP are added to quality
motorcycle oils.
Are you confused yet? These are the two biggest
differences and most costly to distinguish motorcycle oils from
automobile oils. It's safe to say that all motorcycle oils are
somewhat of a synthetic blend. Obviously some more than others
depending on other additives.
If your totally baffled by all of this, don't worry
about it. A good rule of thumb is use motorcycle oil for
motorcycles, automotive oil for automobiles and aircraft oil for
aircraft. Simple as that.