Uniform molecule size and viscosity modifiers

Status
Not open for further replies.
Joined
Sep 9, 2019
Messages
46
Location
SC
When viscosity modifiers are added to a synthetic base oil, say in m1 0w20 ep or 0w40, then at operating temperature are all the molecules of same size ? Uniform molecule size is touted in selling synthetic oils. Are the molecules from the viscosity modifier larger than those of base oils?
 
Last edited:
Not all the same size but probably the distribution curve of molecular weight/size is much narrower for a PAO or a GTL oil than one that is refined from dino drippings.
 
Originally Posted by Rav4H2019
When viscosity modifiers are added to a synthetic base oil, say in m1 0w20 ep or 0w40, then at operating temperature are all the molecules of same size ? Uniform molecule size is touted in selling synthetic oils. Are the molecules from the viscosity modifier larger than those of base oils?

What the heck, I'll take a stab at this. I don't think they are all exactly uniform in size, otherwise you wouldn't have permanent shear loss. So some of the uncoiled VM polymers get chopped up, reducing the VM's ability to resist the flow of the base oils molecules.

Now there are really high quality VM's that better resist this shearing. You see these used in extended drain lubes for example.

( I've read that higher molecular weight VM polymers do a great job of thickening the oil but are more prone to shear (larger size??) and the treat rates are lower when using these high molecular weight VM's. Conversely, low molecular weight polymers are better at resisting shear but not so much at thickening hence the treat rate (quantity needed) is higher)
 
Last edited:
It's a bunch of marketing baloney.

Think about it logically. Molecular size is measured In Angstroms.

1 angstrom = 1/10,000 Microns

1/1000 of an inch or mil is used in engine measurement = 25 Microns

An oil molecule = ~30 Angstroms

The argument that synthetic oils molecular size being more uniform than conventional is completely irrelevant in a fully formulated motor oil when only ~80% is base. VM's are significantly larger - not to mention some of the other hodgepodge of ingredients that may be too.
 
So when synthetic oil with VM''s is being squeezed in between two metal plates, VM''s are providing the padding at operating temperature they are larger ?
 
Last edited:
This goes back to the 70's when I started using synthetic oil; At that time it was stated that dyno oil has 3 types of molecules small-medium & large.

The small & large molecules get burnt off and end up as deposit on your valves and piston head while the medium size ones lubricate.

I'm pretty sure that may not be possible to make all the molecules, no matter the category, uniform in size so there must be an amount of give & take.
 
Last edited:
Originally Posted by Rav4H2019
So when synthetic oil with VM''s is being squeezed in between two metal plates, VM''s are providing the padding at operating temperature they are larger ?


So when synthetic oil with VM''s is being squeezed in between two metal plates, VM''s are providing the padding at operating temperature SINCE they are larger ?
 
Originally Posted by Rav4H2019
So when synthetic oil with VM''s is being squeezed in between two metal plates, VM''s are providing the padding at operating temperature they are larger ?


Now we're getting into pocket protector territory (not meant in the pejorative) of temporary polymer shear. What I understand is this phenomenon always occurs when the oil is squeezed enough between two surfaces for the VM polymers to align themselves like nesting spoons. To what degree of VM type and the base oil viscosity comes into play is the 64 thousand dollar question best answered by more learned members.

For further edification research traction coefficient and pressure viscosity constant on this topic. Very interesting reading.
 
Last edited:
Originally Posted by Pelican
This goes back to the 70's when I started using synthetic oil; At that time it was stated that dyno oil has 3 types of molecules small-medium & large.

The small & large molecules get burnt off and end up as deposit on your valves and piston head while the medium size ones lubricate.

I'm pretty sure that may not be possible to make all the molecules, no matter the category, uniform in size so there must be an amount of give & take.


So the smaller ones burn off as they are more prone to burn off. ? And the larger ones are carrying the load so to speak and hence burn off ?
 
Originally Posted by ndfergy

The argument that synthetic oils molecular size being more uniform than conventional is completely irrelevant in a fully formulated motor oil when only ~80% is base. VM's are significantly larger - not to mention some of the other hodgepodge of ingredients that may be too.

Really?

Setting fully synthetics PAO aside, Grp3 synthetics are hydrocracked.. the breaking of long change hydrocarbons into smaller uniform molecules. The resulting (designer) base oil has superior (to mineral) oxidative and thermal stability, higher VI and the highly processed (cracked) oil has a lower "traction coefficient" (lubricant friction) then grp2 mineral oils because of molecular uniformity.

Some Grp3 base stocks like Shell's GTL rival PAO in performance and some highly processed Grp2+ oils have viscosity indexes approaching Grp3. Chevron for example has a grp2+ with a VI of 118(119??) with a volatility of a grp3.

Synthetics v. Mineral
 
Last edited:
Originally Posted by FordCapriDriver
The whole molecule size thing ( from what i've been able to gather ) is more of a marketing gimmick than anything.


Ditto.
 
I vote Ravenol for the best marketing program. /tongue in cheek

Even if their PDFs like the one linked are pure marketing hooey, it means something to me when a company will spend the time to tell you about its products in greater depth than competitors do. I've used the Ravenol DXG, and it seemed like a good oil other than I got d1G1 oil in a jug labeled d1G2; but since my vehicles don't require either cert, I use it anyway.

I'll be putting it in my Impreza before it snows, replacing some Amsoil SS 10W30.
 
Originally Posted by Mad_Hatter
Originally Posted by ndfergy

The argument that synthetic oils molecular size being more uniform than conventional is completely irrelevant in a fully formulated motor oil when only ~80% is base. VM's are significantly larger - not to mention some of the other hodgepodge of ingredients that may be too.

Really?

Setting fully synthetics PAO aside, Grp3 synthetics are hydrocracked.. the breaking of long change hydrocarbons into smaller uniform molecules. The resulting (designer) base oil has superior (to mineral) oxidative and thermal stability, higher VI and the highly processed (cracked) oil has a lower "traction coefficient" (lubricant friction) then grp2 mineral oils because of molecular uniformity.

Some Grp3 base stocks like Shell's GTL rival PAO in performance and some highly processed Grp2+ oils have viscosity indexes approaching Grp3. Chevron for example has a grp2+ with a VI of 118(119??) with a volatility of a grp3.

Synthetics v. Mineral


I'm not arguing the efficacy of the oil, I'm arguing the marketing of uniform molecules.
 
Originally Posted by Pelican
The small & large molecules get burnt off and end up as deposit on your valves and piston head while the medium size ones lubricate..


So then all the molecules end up the same size and it's as good as synthetic.
 
Originally Posted by Silk
Originally Posted by Pelican
The small & large molecules get burnt off and end up as deposit on your valves and piston head while the medium size ones lubricate..

So then all the molecules end up the same size and it's as good as synthetic.


They will have uniformity (sort of), but not the same size nor the same properties as they will not have the same flash points etc.
 
Last edited:
Originally Posted by Silk
Originally Posted by Pelican
The small & large molecules get burnt off and end up as deposit on your valves and piston head while the medium size ones lubricate..


So then all the molecules end up the same size and it's as good as synthetic.

No, because at the molecular level their still different. In other words the molecules within the lube are different from synthetic to mineral. Higher quality base oils like grp3 and 4 have a higher concentration of "saturated" molecules.

"Saturated molecules contain a higher percentage of carbon-hydrogen (CH) bonds, which limits the available sites to which other, harmful molecules can attach. When other molecules, like oxygen, attach to oil molecules, they break down the molecular composition of the oil and weaken its performance. Saturated molecules are beneficial in lubricating fluids because they remain stable longer, resulting in a more durable lubricant. Unsaturated molecules have fewer single carbon-hydrogen bonds and are therefore less stable"

Synthetics also contain little to no sulfur (contaminant) and wax, which gives synthetics the edge in cold conditions. Synthetics are, in almost every way, superior to a mineral oil. This is not to say that mineral (Grp 2/2+) aren't perfectly suitable for use as an engine lubricant, they are.

Amsoil mineral v. synthetic

[Linked Image]


[Linked Image]
 
Last edited:
Status
Not open for further replies.
Back
Top