Viscoscity / temperature Question

[shanneba]

Looking at the spec sheet for Mobil 1 0W-40 it shows a cSt @ 40C of 0f 80 and 14.3 @ 100C.
I doubt that the cSt is linear.

At what temperature will the oil be the thickest?

 

[XS650]

The colder it gets, the more viscous it gets.

 

[1911]

quote:

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Originally posted by shanneba:
Looking at the spec sheet for Mobil 1 0W-40 it shows a cSt @ 40C of 0f 80 and 14.3 @ 100C.
I doubt that the cSt is linear.

At what temperature will the oil be the thickest?

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The relationship between lube oil viscosity and temperature is mathematically a logarithmic one and thus,plots of the log (base 10) of viscosity versus absolute temperature tend to be fairly linear.

Also, be weary of using the BITOG method of determining the propensity towards more VI by taking the "spread" between the numbers on your oil lable viscosity. For example, a quick viscosity plot of Mobil 1 0W-20 versus 5w30 will show that there is much more likely to be more VII in the 0W-20 with it's 20 point spread than 5w30 with it's 25 point spread.

 

[Quattro Pete]

quote:

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Originally posted by shanneba:
At what temperature will the oil be the thickest?

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At -54 C, because that's when it turns into solid.

 

[Blue99]

Use this link for a Viscosity Calculator to view the viscosity of an oil at various temps.

Use module #4 and plug in 100C, viscosity at 100C, and the VI index - all fround on the product data sheets.

Here's Mobil 1 0W-40, with 14.3 cSt@ 100C & 187 VI index.

code:

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Temp Viscosity

C cSt



-20 2655

0 598

20 192

40 79.8

60 39.8

80 22.7

100 14.3

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At temps below about -20C, for many oils, the increase in viscosity is less linear and the calculator looses accuracy.

 

[shanneba]

using GC 0w30 with a Cst of 12.1 at 100 and 68.5 at 40 and a VI of 179, when I start my car at about 40 C the oil is about a 20 weight oil and it thickens to a heavier 30 weight at 100 C but it is really thinner.