The last time we looked at this at Bitog, we posted examples of auto magazine writers using both terms randomly. It in the mainstream.
Why do people say weight when it’s viscosity?
- Thread starter Fishstyx
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Before motor oil was for gasoline engines the terms Light and Heavy were in common use, this was before viscosity or grade were common descriptors and before the SAE setup standards for what a Light and Heavy oil were.
This 1908 publication uses the phrase light to describe the “grade”
Considering oil is described with terms normally relating to mass it’s no wonder the colloquialism was made by the 1870’s describing one of the three oil “weights”
That’s even a better answer.
Right. As I understand it, it's grade not weight or viscosity.
I’ve said for years that the term weight just confuses people who are trying to learn about engine oil. Or the people who aren’t trying to learn about it are just mixed up. I’ve shared before about when I was at the brake/muffler shop when the tech told me “zero weight oil is too thin, it’ll ruin your engine”. Obviously the guy was a mental midget.
Quite often people think the w in the oil numbers means weight. Wait, what?
Quite often people think the w in the oil numbers means weight. Wait, what?
At the end of the day , does it really matter if they think that ? Will it somehow change which oil they select ? Does it change the characteristics of the oil ? NO to all three ...
No it doesn’t matter just like when people put an R in a word that doesn’t have one like Warsh or warshington state. Or say crick instead of creek. You know what they mean; but you kind of look at them funny and question if their family tree has any branches.
now, now Fishsticks...
Kind of like how it doesn’t matter what people wear no matter the setting?
Well, we say weight when we should say mass so why not use mass for whatever? 
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All I can tell you is that a gallon of 5w-40 is much heavier than a gallon of 0w-20.
I can tell by how sore my arms get from carrying a gallon of 5w-40 from the back of Wal-Mart. I should use lighter oil....
I can tell by how sore my arms get from carrying a gallon of 5w-40 from the back of Wal-Mart. I should use lighter oil....
MolaKule
Staff member
Because mass doesn't describe the flow characteristics of the oil, whereas the viscosity does.Well, we say weight when we should say mass so why not use mass for whatever?
Would one say a kilogram or a pound of molasses or wet cement would have the same flow (viscosity) characteristics as an SAE 5W20 grade oil with 50 cSt viscosity at 40C and a 8.8 cSt at 100C?
Again, an SAE "Grade" describes the Viscosity Range of a lubricant because viscosity describes flow, or more correctly, the resistance of a fluid to flow.
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Weight is a layman's or marketing term while viscosity is used "in the lab" or in the industry.
While do people call engines motors?
MolaKule
Staff member
How can that be?
The typical density of a 0W20 is 0.845 grams/cm^3, and the density of a typical 5W40 is 0.850 grams/cm^3
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MolaKule
Staff member
Because engines and motors are both "sources" of torque.
Weight however has nothing to do with viscosity or the viscosity range of a "Grade."
My point is the term weight is generally misused. No other implication intended. I'm sure you know what they say about making assumptions.
Apparently the idiom “weight of an oil” traces back further than I thought
to the 1700’s as an old timey measurement of the frictional properties of a surface using a measurement called “weight percent” (not the modern definition)
Thank you Coulomb for determining that different lubricants altered the weight percents of a plane in different ways meaning the “weight” of an oil is a real and complex measurement properly referred to as a weight.
“Charles Augustin Coulomb, a French military engineer and physicist, continued to expand on Amontons’ ideas about surface roughness and mixed friction, along with the connection between horizontal force and weight percent”
Merry Christmas, most oddities of language trace back to the original and common language used after invention.
Why is weight the proper description?
Because it’s the only description we ever used.
MolaKule
Staff member
"When unlike charges (one negative and the other positive) attract each other, or like charges (both positive or both negative) repel each other, Coulomb’s law governs the force between them. According to this law the force of attraction or repulsion varies inversely with the square of the distance between the charges. Suppose two particles, one with a charge of +1 μC (microcoulomb) and the other with a charge of –1 μC are placed 1cm apart. The force of attraction between these two charges is found to be 90 N (newton), about the same force as gravity exerts on a 20-lb weight. If the distance between the charges is now multiplied by a factor of 100 (increased to 1 m), then the force of attraction between the two charges is found to be divided by a factor of 100 squared, i.e., by a factor of 104. Consequently the force decreases to about the weight of a grain of sand."
Here, they are speaking to the Force equivalents of gravity, the same force as gravity would exert on a XX-lb weight.
Physicist Isaac Newton trumps mathematician Euler and engineer/physicist Coulomb with the term "Viscosity."
"In 1687, Sir Isaac Newton, an English physicist and mathematician, defined the term “viscosity,” which centered on the belief that friction had both molecular and mechanical causes. Viscosity today can be defined as “the state of being thick, sticky, and semifluid in consistency, due to internal friction.” Newton had the right idea and the correct terminology.
So the term "Viscosity" came about 150 years before "Weight."
Here, they are speaking to the Force equivalents of gravity, the same force as gravity would exert on a XX-lb weight.
Physicist Isaac Newton trumps mathematician Euler and engineer/physicist Coulomb with the term "Viscosity."
"In 1687, Sir Isaac Newton, an English physicist and mathematician, defined the term “viscosity,” which centered on the belief that friction had both molecular and mechanical causes. Viscosity today can be defined as “the state of being thick, sticky, and semifluid in consistency, due to internal friction.” Newton had the right idea and the correct terminology.
So the term "Viscosity" came about 150 years before "Weight."
I took that as sarcasm, you are correct the differing weight of the containers is not going to be noticeable.
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