# Calculating oil viscosity at various temperatures.

#### OilUzer

I used the Andrade correlation method/calculator to calculate the viscosity of couple of oils at 0C (32F). Refer to the links below for the calculator and Andrade correlation method. plugged in data from the following 2 oils (same brand). Nothing specific about these oils just that I currently have the 10W in the garage. both are full synthetic. Was just curious about 0W viscosity near freezing ... Data from the oil company: Oil 1 - 10W30: KV100 = 11.60 , KV40 = 71.54 Oil 2 - 0W30: KV100 = 12.18 , KV40 = 73.21 Note: Oil #2 is A3/B4 Calculated viscosity at 0C (32F) is: Oil 1 : 657.35 cSt Oil 2 : 637.60 cSt Calculated viscosity at -17.78C (0F) is: Oil 1 : 2879.79 cSt Oil 2 : 2667.69 cSt Not a huge viscosity diff between a 0W A3/B4 and a 10W30 at freezing 0C (32F). Q: is this a very accurate method to estimate or calculate the viscosity? Any other method you guys use? viscosity calculator: Viscosity calculator info from the above web site: "Calculate the viscosity at a given temperature, when the viscosity is known at two temperatures. The viscosity of a liquid as a function of temperature can be approximated with the Andrade correlation. Given two known temperature-viscosity points, the viscosity of a liquid can be calculated for a target temperature. Lubricating oil producers normally publish the viscosity of their products at two different temperatures. ... The calculator can be a useful tool for predicting viscosity at a target temperature, but keep in mind that in real world applications a theoretical viscosity value should always be verified with a viscosimeter." Additional info from petrowiki: Oil Viscosity "Andrade's method is based on the observation that the logarithm of viscosity plotted vs. reciprocal absolute temperature forms a linear relationship from somewhat above the normal boiling point to near the freezing point of the oil, as Fig. 6 shows. ..."

#### burla

It is good to use for towing as well, I know a guy who has a pull over temp because how thin oil is at 250f. He can't go really thicker as it is in a mds engine, but he smartly used a graph and when the range was too thin for his liking, he pulls over and let's it cool.

#### benjy

from reading graphs show real synthetics group IV + V oils thin slower in the heat + even more so thicken less as temps drop, hence the the use of costly group IV PAO + V Ester in extreme conditions like Alaska or a race application!

#### OVERKILL

##### \$100 Site Donor 2021
Originally Posted by OilUzer
I used the Andrade correlation method/calculator to calculate the viscosity of couple of oils at 0C (32F). Refer to the links below for the calculator and Andrade correlation method. plugged in data from the following 2 oils (same brand). Nothing specific about these oils just that I currently have the 10W in the garage. both are full synthetic. Was just curious about 0W viscosity near freezing ... Data from the oil company: Oil 1 - 10W30: KV100 = 11.60 , KV40 = 71.54 Oil 2 - 0W30: KV100 = 12.18 , KV40 = 73.21 Note: Oil #2 is A3/B4 Calculated viscosity at 0C (32F) is: Oil 1 : 657.35 cSt Oil 2 : 637.60 cSt Calculated viscosity at -17.78C (0F) is: Oil 1 : 2879.79 cSt Oil 2 : 2667.69 cSt Not a huge viscosity diff between a 0W A3/B4 and a 10W30 at freezing 0C (32F). Q: is this a very accurate method to estimate or calculate the viscosity? Any other method you guys use? viscosity calculator: Viscosity calculator info from the above web site: "Calculate the viscosity at a given temperature, when the viscosity is known at two temperatures. The viscosity of a liquid as a function of temperature can be approximated with the Andrade correlation. Given two known temperature-viscosity points, the viscosity of a liquid can be calculated for a target temperature. Lubricating oil producers normally publish the viscosity of their products at two different temperatures. ... The calculator can be a useful tool for predicting viscosity at a target temperature, but keep in mind that in real world applications a theoretical viscosity value should always be verified with a viscosimeter." Additional info from petrowiki: Oil Viscosity "Andrade's method is based on the observation that the logarithm of viscosity plotted vs. reciprocal absolute temperature forms a linear relationship from somewhat above the normal boiling point to near the freezing point of the oil, as Fig. 6 shows. ..."
Keep in mind, calcs stop working much below 0C. At that point, you can look at CCS and/or MRV and halve the viscosity to step it back to the grade you are comparing it with. This will give you a better idea.

#### OilUzer

Originally Posted by OVERKILL
Keep in mind, calcs stop working much below 0C. At that point, you can look at CCS and/or MRV and halve the viscosity to step it back to the grade you are comparing it with. This will give you a better idea.
Q: Are these calculation pretty accurate or just a guesstimate? It was interesting that a 0W and a 10W have a very close viscosity at 0C and not a huge diff even at 0F. Also what's up with the statement below "linear relationship From boiling to freezing point of the oil ...". iirc, oil doesn't technically freeze. Is that a typo? Based on that statement, you would think the calculator should work below 0C. From petrowiki: "Andrade's method is based on the observation that the logarithm of viscosity plotted vs. reciprocal absolute temperature forms a linear relationship from somewhat above the normal boiling point to near the freezing point of the oil, as Fig. 6 shows. ..."

#### Lowflyer

Originally Posted by OilUzer
Are these calculation pretty accurate or just a guesstimate?
If you know "allowed" tolerances for each batch and day in fabrication, you dont would ask a questions about "pretty accurate"

#### OVERKILL

##### \$100 Site Donor 2021
Originally Posted by OilUzer
Originally Posted by OVERKILL
Keep in mind, calcs stop working much below 0C. At that point, you can look at CCS and/or MRV and halve the viscosity to step it back to the grade you are comparing it with. This will give you a better idea.
Q: Are these calculation pretty accurate or just a guesstimate? It was interesting that a 0W and a 10W have a very close viscosity at 0C and not a huge diff even at 0F. Also what's up with the statement below "linear relationship From boiling to freezing point of the oil ...". iirc, oil doesn't technically freeze. Is that a typo? Based on that statement, you would think the calculator should work below 0C. From petrowiki: "Andrade's method is based on the observation that the logarithm of viscosity plotted vs. reciprocal absolute temperature forms a linear relationship from somewhat above the normal boiling point to near the freezing point of the oil, as Fig. 6 shows. ..."
They will be "reasonably close" provided the input data is accurate. But Lowflyer's point is valid, batch variation is a thing. Regarding your 2nd query: Yes, oil freezes. Long answer: Conventional and Group III bases contain wax, as the temperature drops these waxes form crystals, which causes it to gel. Pour Point Depressants (PPD's) are added to oils blended with these bases in order to mitigate this effect, and, as the name implies, driving down the temperature at which the oil will no longer pass CCS/MRV for the grade in question. One you are in this realm, which doesn't have to be all that cold, depending on the base used, the behaviours will not follow the calculator. We've seen the odd data sheet where visc is provided at other temperatures and the calculated value is WAY off. Secondly, PAO doesn't have any slack wax in it, ergo, it isn't susceptible to the same effect. However, the additives added to it of course are. Mobil has PDS sheets for their myriad PAO base oil offerings, if you want to see how close the calc is on a virgin base, run it on a few of those, as they provide KV at additional temperatures on these sheets: