At 08:25 PM 1/20/2000 -0500, you wrote:
>Mike Schwall wrote:
> > You may notice more audible gear noise with the synthetic. Now I
> > could put on my chemistry hat and preach about the molecular difference,
> > but I'll save the disk space :) I wonder how many eyes rolled on that
> one :)
> >
> > Mike
>
>I wanna know, if you wouldn't mind. I noticed some more gear noise in
>my 5-speed when I went to synthetic. I thought I hadn't filled it
>completely at first. I've been wondering if it was the synthetic that
>was causing it, and why.
>Jason
I was edging to the discussion of synthetic versus dino juice, and what
makes synthetic better, and what makes a synthetic oil better than another
synthetic oil.
In your case it's kind of simple once you get familiar with it. Synthetic
oil, no matter what weight, will be more fluid at a wider range of
temperatures than dino juice. Regular organic oil (dino juice) is refined
to a certain base weight, then viscosity modifiers are added to create
multi-weight oil and to maintain proper viscosity over a certain
temperature range. I'm not a chemistry professor, so I won't go into
details about the chemical makeup. What the difference is between the two
are that dino juice has a very narrow range of fluidity. Dino juice is
very sensitive to temperature changes. When cold, the dino juice flows
very slowly. That is why for colder weather, you have 5W oil, the base
stock is very thin. Then viscosity modifiers are added to make a
multi-weight oil. As the oil heats up, the viscosity modifiers create
molecular chains which make the oil thicker. Only problem with dino juice
is the molecular bonds that create the chains are not strong. Heat and
stress will cause the modifiers to break down and make the oil revert back
to it's original base weight. Which is not good. Imagine running your
truck down the highway at 75MPH doing 2000+ RPMs when it's 90+ degrees F
outside pulling a heavy trailer and you've got 10 weight oil in your
engine. (10W-30). So we change the oil every 3000 miles. For you northern
folks, thin weight is desired. You don't have to worry about the oil
breaking down because your not stressing your oil with high heat, and you
get oil pressure and oil flow.
Now to synthetic. There are two different types of synthetic oil
bases. One is a synthesized hydrocarbon base, and the other is a
diester/polyester base which is basically a plastic/polymer base
oil. What's the difference? Synthesized hydrocarbon base is the same
hydrocarbon base used in regular dino oil, except it was made in a lab not
by nature. It's a copy of nature. This synthetic base is much stronger
than the organic, and it doesn't break down as easily as the real stuff and
it's more stable through a wider temperature range. This allows it to flow
at very cold temperatures and flow really well at higher temperatures
without thermal breakdown. Even though it's the same weight as dino, it
will be much "thinner" at any given temperature. Mobil 1 uses a
synthesized hydrocarbon base. Both in their engine oil and gear oils. The
oil will still break down, just not as soon and as easily as organic. That
is why the manufacturers say you can extent oil changes to 6000 miles or so.
Your diester/polyester oil is the only true synthetic oil. It is a totally
artificially made oil. It is basically a plastic oil. It will NEVER break
down. Only reason this type of oil has to be changed is because there is
no way to filter it enough to keep it as pure as it was before it was
poured. Only manufacturers of true diester/polyester base oils that I know
of are NEO, Torco, and Red Line. I tried to contact AMSOIL in the past,
but I never received a reply with a direct answer about the base used in
their oils. From their specs on pour point, flash point, and viscosity
index it looks the same as Mobil 1. Food for though, NEO lubricants are
used by the top NASCAR, CART, Formula I and NHRA teams as well as SCCA and
PSR competitors. Cost? One quart of 10W-30 costs $10. That's for the
absolute best stuff you can get. I actually have NEO 75W-90HD in the rear
end of my old Ferd which has all new Timkin bearings, Genuine Gear 3.89:1
gears and a Detroit TruTrac LSD differential. That cost me $10 a quart
times four.
Now to answer your original question, finally :) The reason you hear more
gear noise is because the synthetic oil is thinner which allows the oil to
splash around and run off the gears quick, but still provide excellent
lubrication, because it's so thin. When gears are meshed together they
will create harmonics which if not absorbed by something, will become
audible. With dino juice, the oil is "thick" enough to absorb the
harmonics created by the metal to metal contact of the meshed gears. With
synthetic, the oil is much "thinner" and won't absorb the harmonics as well
as the organic oil. If you went to a thicker weight synthetic, you will
reduce the amount of audible gear noise. That is why they sell 80W-140 in
both dino and synthetic. It's more for heavy duty situations where high
ambient temperatures and heavy loaded vehicles will break down thinner dino
juice pretty quick and cause gear failures.
Off to another point. Aftermarket gear sets are not alike. Every
manufacturer uses a different hardness of steel in their gear sets. The
harder the steel, the louder the gear set will be when in operation. Most
of your racing gears such as what you will get from Richmond Gear are very
loud gears, even when set up properly. The harder steel used in these
gears make them stronger and less prone to breakage when you transfer high
torque loads such as in a drag race vehicle.
I have researched, in the past, different synthetic oil manufacturers and
their oils. I have a list of the manufacturers I mentioned with their web
site urls and the technical info. Email me if you want a copy of it.
Hope this helped,
Mike
__________________________
mschwall@flash.net
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