Oil Density

Shel_B

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Looking at various Data Sheets, I see density mentioned as a characteristic. The density figures I've seen all seem to be about the same, similar but not always identical.

What aspects of an oil contribute to its density, especially the small differences between brands and blends, and how does the density affect its performance?
 
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What aspects of an oil contribute to its density, especially the small differences between brands and blends, and how does the density affect its performance?
Specific gravity of the components determine the final density.

Nothing with regard to performance should be inferred from a density value unless that value is wildly out of the ordinary.
 
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The density of the finished product is going to be determined by everything that goes into the blending of the final product. The individual base oils, and all the different additives and co-solvents (if necessary) to dissolve the additives.
 
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Since the base oils used make for the majority of the formulation their specific
weight is also the dominant factor for the specific weight of the final product.

If interested jus compare Exxon's base oil offerings.
 

Shel_B

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Thanks, guys!
Wonder why density is listed at all on Mobil's or other's websites? Doesn't seem to be useful information to a consumer.
Color is also listed ... interesting, but of any real importance? I'd much rather see HT/HS and NOACK more regularly.
 

ZeeOSix

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Water is more dense than motor oil, yet the viscosity of water is much lower. Lubrication performance not a density parameter.
 

ZeeOSix

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You need it to convert from kinematic viscosity to dynamic viscosity. Winter tests depend on dynamic viscosity as does HTHS but viscosity for SAE grading is kinematic.
The density or specific gravity spec is given at room temperature. It wouldn't be useful in calculating a HTHS ... that has to be measured.
 
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Wonder why density is listed at all on Mobil's or other's websites? Doesn't seem to be useful information to a consumer.

Some ingredients in motor oil are sold by volume (gallon/barrel), some by weight (pound/kilogram/metric ton). Also some companies keep their records in volume and some in weight. Density allows easy conversion between volume and weight, and is also a quality control statistic. Color is more of a quality control measurement. Neither reflects oil performance but can be useful in the business end.
 
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Thanks for your responses everyone. I hadn't thought of the commercial applications for listing density, but was looking at the listed densities from the average consumer's point of view. Now I understand why they are listed.
 

ZeeOSix

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Not really, density chasnges predictably enough with temperature.
You still couldn't determine HTHS even if you could accurately determine the density at 150C because the HTSH is highly dependent on the shear rate.
 
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