You were wrong then, and you are wrong now if you think that the time
you hold the fluid at a given temperature matters. The thickness
measurements are taken *after* the fluid stabilizes at a given temperature.
Both Scott and I have said this. You are still missing the point. If you
plot the curve of thickness vs temperature (no "time" axis comes into
play), the viscosity index is the SLOPE of that curve. Different oils
have different slopes (change thickness LESS as the temperature
changes), and the less steep the slope the higher the VI and the wider
the multi-viscosity rating can be.
NOTE: That FLUIDS (and NOT solids as you gave an example) behave
Let's start here since notation doesn't transfer to non-binary groups.
If a compression or expansion takes place under constant temperature
conditions - the process is said to be isothermal. The isothermal process
can with the Ideal Gas Law be expressed as
p / ρ = constant (1)
p = absolute pressure
ρ = density
physics) The dimensional changes exhibited by solids, liquids, and gases for
changes in temperature while pressure is held constant.
Most materials are subject to thermal expansion: a tendency to expand when
heated, and to contract when cooled. For this reason, bridges are built with
metal expansion joints, so that they can expand and contract without causing
faults in the overall structure of the bridge. Other machines and structures
likewise have built-in protection against the hazards of thermal expansion.
But thermal expansion can also be advantageous, making possible the workings
of thermometers and thermostats.
How It Works
Molecular Translational Energy
In scientific terms, heat is internal energy that flows from a system of
relatively high temperature to one at a relatively low temperature. The
internal energy itself, identified as thermal energy, is what people
commonly mean when they say "heat." A form of kinetic energy due to the
movement of molecules, thermal energy is sometimes called molecular
Temperature is defined as a measure of the average molecular translational
energy in a system, and the greater the temperature change for most
materials, as we shall see, the greater the amount of thermal expansion.
Thus, all these aspects of "heat"—heat itself (in the scientific sense), as
well as thermal energy, temperature, and thermal expansion—are ultimately
affected by the motion of molecules in relation to one another.
Molecular Motion and Newtonian Physics
In general, the kinetic energy created by molecular motion can be understood
within the framework of classical physics—that is, the paradigm associated
with Sir Isaac Newton (1642-1727) and his laws of motion. Newton was the
first to understand the physical force known as gravity, and he explained
the behavior of objects within the context of gravitational force. Among the
concepts essential to an understanding of Newtonian physics are the mass of
an object, its rate of motion (whether in terms of velocity or
acceleration), and the distance between objects. These, in turn, are all
components central to an understanding of how molecules in relative motion
generate thermal energy.
The greater the momentum of an object—that is, the product of its mass
multiplied by its rate of velocity—the greater the impact it has on another
object with which it collides. The greater, also, is its kinetic energy,
which is equal to one-half its mass multiplied by the square of its
velocity. The mass of a molecule, of course, is very small, yet if all the
molecules within an object are in relative motion—many of them colliding
and, thus, transferring kinetic energy—this is bound to lead to a relatively
large amount of thermal energy on the part of the larger object
Duhhh that's what I said. The molecular CHAINING in multi-weight oils do
NOT change fluid properties, they alter only the TIME frame in which the
changes occur. In other words - when the fluid (in this case motor oil)
absorbs heat from the engine, a 10 W. 30 weight oil will thin to equivalent
of a 10 weight oil in a longer span of time than a straight 30 weight would.
But when both fluids attain the destination temperature their viscosity will
be essentially the same as will their lubrication potential. The standard
test for lubrication potential of motor oils has been for many decades to
heat them to a specific temperature akin to the operating temperature of a
motor oil in an average internal combustion engine. Then to apply pressure
to bearings on a rotating shaft to determine at what point the oil loses its
lubrication potential. Texaco for some years was running a TV ad comparing
their Havoline 10 W 30 against other oil companies 10 w 30. My argument with
the refinery engineer was along the lines that I thought Havoline straight
30 weight would actually perform better than the multi-grade. He said that
they had never compared it to our own oils. He then performed the tests in
the Texaco labs. He bought me the steak dinner.
That was before 10 W 40 and 10 W 50 came around and later 20 W 50. Long
before synthetics which has a very improved lubrication potential. Recently
Castrol's Edge deposed Mobil 1 as the champ.
By a remarkable degree. I am sure that Mobil won't take that sitting down.
<irrelevant discussion snipped>
I never mentioned any solid and neither did Scott- he mentioned a
What I have said is that the rate of change of thickness with
temperature is different for different base oils. For example, shell
XHVI Group III+ base oil (Rotella synthetic, Pennzoil Platinum) thins
out FAR less as you heat it up than a garden-variety group II or III
base oil (plain old Valvoline or Castrol non-synthetic, Pennzoil "yellow
bottle", etc.) even before you start putting in additives. If you still
deny this fact, then you're still wrong.
Its just like my water vs. honey example. Honey changes thickness a lot
as you warm it up, water hardly changes at all. The XHVI base oil is
more like water in that regard. So are the Group IV PAO base fluids that
other synthetics like Mobil 1, Redline, Royal Purple, etc. use. And
THAT is why multi-grade motor oils made from high VI base oils are
superior to single-grade oils.
No that's NOT what you said. And look: you're about to say the same
wrong thing again:
By definition a 10w30 and a 30 will be approximately the same thickness
AT OPERATING TEMPERATURE (the rating is made at 100C). What matters is
the fact that one thins out as you warm it up from a cold start (30 wt),
the other more nearly stays constant (10w30).
Besides that, many modern multi-weight oils DO NOT DEPEND on what you
call "molecular chaining" additives in order to achieve their thickness
stability- it is just inherent in the base oil that it does not thin as
much when you heat it as an older oil.
And with or without "chaining," you are missing the point that time is
irrelevant. If you take a 10w30 oil and a 30 weight oil and hold them at
40 degrees C for a whole year before you measure the thickness, the 30
weight oil will be far, far thicker than the 10w30. Conversely, if you
hold them both at 100 degrees C for a year and then measure the
thickness, they will be about the same thickness. "Time" is irrelevant!
The slope of the thickness/temperature plot is the issue.
Here, go read this thread:
No your wrong about that. The specification does not require them to be exactly
the same but that only the difference to be within a specified amount. At 110C
the difference in viscosity becomes significantly larger. 110C or higher would
not be an unusual temp for oil in the average car on warm summer day. I don't
know if that is what krp is trying to say or not. He is correct that 10w30 will
be thinner than straight 30 in the typical car on a typical summer day.
The point I made was this. Using the identical benchmark testing that
Texaco and independent labs used to compare Havoline 10 w 30 to other major
brand 10 w 30 oils that showed a slight advantage to Havoline, when coaxed
to compare Havoline 10 W 30 to Havoline straight 30 - the straight 30 had a
significant advantage. What wasn't much discussed was some testing Shell did
with identical motors with very sensitive temperature sensors. Engines that
were run for thousands of hours. The multiweight oils did not fare well at
all. The "stress" testing is still the benchmark for testing oil. To this
point, the new Castrol Edge is by a significant margin the best performing
oil on today's market. But as I said, do not expect Exxon Mobil to take this
laying down. Like Arnold - they'll be back with an even better oil.
Better living through chemistry.
That is _simply_ _not_ _true_.
In just about 30 seconds of web searching, I found the spec page for
Royal Purple oils (I'm not promoting RP oils, just found this example
and they are API certified oils unlike some other botique synthetics).
At 100C (the benchmark temperature), their 5w30 oil has a viscosity of
11 centistokes, but their straight SAE 30 is *thinner* at 10.6
centistokes! And their 10w30, while thinner than the 5w30, is still
slightly thicker than the straight 30 weight, at 10.8 centistokes.
Furthermore, the 5w30 has a VI of 157, but the SAE 30 only has a vI of
119, which tells me that you can go WAY above the benchmark temperature
and the 5w30 will remain thicker than the SAE 30.
Here's the link, knock yourself out:
click "Product Sheet" for the PDF.
Well no it simply is and was true. Your originally statement that at operating
temperature the viscosity of 10w30 is the same as 30 w is still false. Does that
mean you can't google and find some oil company advertisement. Well of course
you can find advertisements no body said you couldn't.
Your original statement is still false. Most of the 30 weight oil tends to
have higher viscosity than most of the 10w30 at operating temperature. This is
not speaking of some ideal car and oil. It is just how things generally work in
the real world where most of the cars on the road don't use synthetic oil and
many operate with oil temps higher than 100c on hot days.
**There is a allowable range for viscosity at the standardized temps.
**The economics physical realities of producing motor oils for sale puts most of
the 10w30 at the bottom of the allowable viscosity range and the 30w at the top.
**Most engine oil operates at a temperature above 100C on hot summer days
Those facts combined make it generally incorrect to state (as you did) that the
30w and 10w30 oil will have the same viscosity at operating temperature.
I never actually said that, I said that they would be "approximately"
the same, and that means that the 30 could be either thinner or thicker
than the 10w30 at operating temperature, depending on where operating
temperature falls in relation to the SAE benchmark temperature.
You, however, claimed that (quoting from text reprinted above), "He is
correct that 10w30 will be thinner than straight 30 in the typical car
on a typical summer day," and that is what is categorically false. If
you assume that the 30 and 10w30 are within a small percentage of the
same viscosity at the benchmark temperature, then the 30 will have to
be *thinner* than the 10w30 as you go above the benchmark temperature
because it has a lower viscosity index (in other words, a steeper slope
to its temp. vs. viscosity curve).
That much is just math.
Specification sheet, not advertisment. And you can go look up similar
numbers for Pennzoil Platinum, Castrol Syntec, GTX, Edge, Mobil 1, Mobil
conventional, Kendall, Delo, Rotella, etc. etc. Brand doesn't matter.
See above, this is the part of your argument that is the most incorrect.
It is in fact, generally backwards. You seem to think that 30 weights
will stay thicker at higher temperatures, but the opposite is in fact
true. The simple combination of the fact that the 10w30 and 30 wt. have
to be pretty close in viscosity at the benchmark temperature, and the
fact that the 10w30 has a higher VI *generally* means that the 30 wt.
will be significantly THINNER than the 10w30, not thicker, at
temperatures above the benchmark point. It will be thicker when the
engine is COLDER than the benchmark temperature.
What makes things interesting is that today it is quite possible to
formulate a synthetic oil that meets the requirements for, say, a 10w30
rating and to do it *without* any viscosity index improvers at all.
Synthetic base stocks in both group III+ (eg, Shell XHVI base used in
Rotella and Pennzoil Platinum and similar stock used by Valvoline and
others) and group IV (such as PAOs used by Mobil, Royal Purple, Amsoil,
Shaeffers, etc.) have inherent VIs of 140 and higher now. That means
that the oil company could, if they wanted to, sell it as a 30 weight as
well. And if they do have to add some VIIs to create a multigrade oil
of, say, 5w40, then the amount needed is so extremely small that there's
very minimal benefit, if any, to the single grade oil. Its not like the
old days where making a 10w40 required such a large percentage of VIIs
that they, not the base oil, dominated the deposit formation and
degradation characteristics of the product.
So you keep saying. Dig that hole deeper if you want, I'm done.
No, I believe it both because the math predicts it and because
measurements prove it. If you don't believe me, go over to one of the
oil forums and pose the question. Make it simple, ask them if a 30wt
will be thinner or thicker than a 10w30 at temperatures significantly
I'm done beating the dead horse, Jim. You can have the last word now if
it'll make you feel better.
The math is based on a simplistic model that is little more than taking 2 points
and drawing a line thru them. The model is designed to do not much more than
prove a claim to the simple minded and it does that as long as one is willing to
completely ignore the real world.
What measurements? You have provided only 2 measurements for one particular
brand and that comes with a caveat that you may see some variance from the
measurements in the actual product. You are talking about one particular brand
of synthetic that has a tiny tiny share of the market. That is pretty thin soup
you are calling proof.
?If you don't believe me, go over to one of the
OK, I swore I wouldn't respond again, but this is just too much.
>The math is based on a simplistic model that is little more than
taking 2 points
>and drawing a line thru them.
Its not a line, its a curve.
But apart from that the "simplistic model" also happens to be EXACTLY
correct for a Newtonian fluid, which is precisely what defines a
straight-grade oil (no viscosity index improvers are permitted in
straight-grade rated oils). Therefore, the only deviation from the model
in the "real world" will be for the non-Newtonian fluid, which the
multi-grade may or may not be depending on whether it has VII additives
or not. Assuming it does, then it's viscosity will always be higher at
high temperatures and lower at low temperatures than the Newtonian fluid
up to the temperature at which the VIIs disintegrate, but by then both
oils are oxidizing as well! Assuming that it does not have VIIs, then
the "2 point" model is also correct for *it* at the high end (the low
end may still be non-Newtonian because of pour-point depressant
additives) and the two curves will never cross again above the
temperature at which the two fluids have equal viscosity (which in the
example is already BELOW the 100c benchmark).
Chosen only because they make their data readily available and popped up
first on a Google search. It also happens to be representative of all
PAO-based synthetics in this regard, there's nothing special about it.
In fact in doing a little more research, that brand's multi-grade oils
are apparently considered in the thin side and prone to shearing for
their rating, so in that sense they are a bad case for my argument. Pick
any brand you want, or pick a different brand of straight from
multi-grade. Go ahead. Find a counter-example! Please! Its quite likely
that you can find at least one combination of oils that meet your
criteria, especially since so many of the synthetic single-grades could
easily qualify as multi-grades if dual rating were allowed. I didn't
find such an example, but then I didn't go looking very hard for the
oddball counter-example that may be out there.
At least I produced actual numbers instead of just waving my hands and
saying the same thing over and over Lloyd Parker style. Or talking about
how you "notice it when it drains out of the pan," which means that its
already well below the 100C benchmark for one thing, and I seriously
question your eyeballs as an accurate measure of viscosity for another.
If my soup is thin, yours isn't even soup yet.
I'm really done this time.
Right it is a curve not a line. And you haven't a clue as to what the formula
for the curve is in reality. But that doesn't stop you from pretending you are
making a mathematical calculation. All you have really done is read some glossy
brochures and are parroting the buzzwords that you read therein.
What an idiot. If you actually did have even a smattering of understanding of
the math you would recognize that I am saying the 2 curves never cross - that is
in most comparisons the 30 weight is always going to be thicker than the 10w30
at any temp that you might find in an engine crankcase. I don't know (and
neither do you) what the formula is for either curve but it is obvious that they
do not intersect.
Since you don't actually have a precise formula for the curve for either type
of oil it is just babbling nonsense when you claim you can prove your point
Maybe for some particular well chosen examples it will cross at a point below
100C. But in general if you compare what is most commonly available on the
market and what is commonly used in engines that won't be the case.
It is not as if all oil comes in perfect discrete steps of 10 20 30 40 weights.
These are categories describing a range. And even in your fancy brochure that
you offer as proof, there is a disclaimer to that effect.
Nothing special except it is not what is in most engines on the road. And in
part that is why it costs more than what most people use.
You mean I should go find my own glossy brochures?
Who is loyd parker? Another wannabee mathematician?
I'm not the one that made the bogus claim with nothing believable to back it up.
I'm perfectly happy with the information I get from observing a pressure gauge
or watching as it pours thru an opening. You on the other hand keep insisting
that the crap you read in glossy brochures is mathematical proof. Did it ever
occur to you that no company ever puts anything but the information that casts
them in a good light in their advertising literature? So if a company does make
a product that is a cut above average they are going to try to promote that as
selling point and put it in their advertising.
How many miles and years on the engine. If it's a long time I would
just switch to 5w30 non-synthetic. Running synthetic in an old engine
could cause it to start leaking. For those cold northeast mornings
just install a block heater and solve any cold start worries.
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