Viscosity @ 100°C

[Hogwash]

Someone educate me on this measurement at 100°C I see lot when I'm reading oil specs.

It's my understanding that the higher the number, the "thicker" the oil is at that temperature.

So when reading about 2 different oils.....one is 10.8 vs 11.9 for the other....the 11.9 is the thicker oil at temperature. But my question is about the difference in those. Is a 1.1 difference considered a lot? Or is that gap not that much? I don’t have any context to compare the numbers.

 

[kschachn]

Well you have the range for a given viscosity grade, that would give you a general idea of what is significant or not.

 

[Hogwash]

Could you elaborate on that?

 

[RDY4WAR]

The difference between 10.8 and 11.9 is not a lot.

Each oil grade must fall within a certain specified kinematic viscosity @ 100*C (KV100) in centistokes (cSt) per SAE J300.

xw-16 = 6.1-8.1 cSt
xw-20 = 6.9-9.2 cSt
xw-30 = 9.3-12.4 cSt
xw-40 = 12.5-16.2 cSt
xw-50 = 16.3-21.8 cSt
xw-60 = 21.9-26.0 cSt


An oil with a KV100 of 10.8 cSt and another with 11.9 cSt would both be 30 grade oils as they both fall within the range specified by SAE J300.

 

[Hogwash]

The difference between 10.8 and 11.9 is not a lot.

Each oil grade must fall within a certain specified kinematic viscosity @ 100*C (KV100) in centistokes (cSt) per SAE J300.

xw-16 = 6.1-8.1 cSt
xw-20 = 6.9-9.2 cSt
xw-30 = 9.3-12.4 cSt
xw-40 = 12.5-16.2 cSt
xw-50 = 16.3-21.8 cSt
xw-60 = 21.9-26.0 cSt


An oil with a KV100 of 10.8 cSt and another with 11.9 cSt would both be 30 grade oils as they both fall within the range specified by SAE J300.

Got it. Thank you

 

[wbwanzer]

Thanks for posting the viscosity ranges.

 

[KL31]

I'd consider oils on the edge of specs as a bigger difference. Some Euro spec 30 grades will be something like 12.3cSt and some "resource conserving" 30 grades might be 9.4cSt. In that respect, there's two oils in the same grade but quite close to being almost 40 grade and almost 20 grade respectively.

 

[viscous]

Note that viscosity differences become larger as oil cools. That is, for a given selection of oils, the viscosities @ 40°C generally have greater spread than the viscosities @ 100°C.

 

[weasley]

Note that viscosity differences become larger as oil cools. That is, for a given selection of oils, the viscosities @ 40°C generally have greater spread than the viscosities @ 100°C.

That depends on the VI. At a constant VI, whilst the absolute difference will be larger, the relative differences will be the same. If VIs are different then of course the relative differences at 100°C and 40°C will change.

 

[Hogwash]

So to expand on this a bit....I would think a heavier oil (within a particular range) would be an important element to a high mileage formula. For example, M1 HM is heavier than VML.

Is that dated thinking? Is there a benefit to looking for the heaviest oil in a recommended range....in my case 5/30?

 

[RDY4WAR]

I would say the difference between a "light" 30 grade and "heavy" 30 grade is too small to make any appreciable difference in the real world. A 10°C change in oil temp makes as much or more of a difference. Also note that just because an oil starts with a higher KV100, within the same grade, doesn't mean it stays there. I'd take a 10 cSt oil that's shear stable over a 12 cSt oil that shears.

 

[madeej11]

The difference between 10.8 and 11.9 is not a lot.

Each oil grade must fall within a certain specified kinematic viscosity @ 100*C (KV100) in centistokes (cSt) per SAE J300.

xw-16 = 6.1-8.1 cSt
xw-20 = 6.9-9.2 cSt
xw-30 = 9.3-12.4 cSt
xw-40 = 12.5-16.2 cSt
xw-50 = 16.3-21.8 cSt
xw-60 = 21.9-26.0 cSt


An oil with a KV100 of 10.8 cSt and another with 11.9 cSt would both be 30 grade oils as they both fall within the range specified by SAE J300.

I guess his question is, in your example is that 1.1 cSt difference significant within that grade or is it trivial?

 

[edyvw]

I would say the difference between a "light" 30 grade and "heavy" 30 grade is too small to make any appreciable difference in the real world. A 10°C change in oil temp makes as much or more of a difference. Also note that just because an oil starts with a higher KV100, within the same grade, doesn't mean it stays there. I'd take a 10 cSt oil that's shear stable over a 12 cSt oil that shears.

Take a look at HTHS of those two oils.
ALso, Euro W30 oils are more shear stable than ILSAC GF oils.

 

[edyvw]

I guess his question is, in your example is that 1.1 cSt difference significant within that grade or is it trivial?

It could be. It depends on other indicators such as approvals. 11.9cst is probably Euro W30 oil. That means high HTHS, more stringent stay in grade requirements. Some Euro W30 oils have HTHS that is on par with W40 oils. So yeah, difference will be noticable.

 

[bruce381]

makes no difference in end use. A 1.1 cSt difference in a oil will not matter fuel dilution or oxidation will be make more change then that.
unless you are calibrating a vis machine not an issue.

 

[Hogwash]

I guess his question is, in your example is that 1.1 cSt difference significant within that grade or is it trivial?

Yes.....exactly

 

[Hogwash]

Thank you gentleman. That's why I come here. I suppose in the end it won't matter at all what I go with. The M1 HM seems heavier than most other 5/30s. So if availability and cost are equal among the big brands I might as well go with it.

Currently have M1 T&S awaiting my next change in about 1k miles. So I'm several months away. But after that I may give the M1 HM a try

 

[Hogwash]

....I'd take a 10 cSt oil that's shear stable over a 12 cSt oil that shears.

How would one know how shear stable an oil is? M1 HM or Valvoline full synthetic Maxlife, both 5/30.....which would win that contest?

 

[mahanddeem]

How would one know how shear stable an oil is? M1 HM or Valvoline full synthetic Maxlife, both 5/30.....which would win that contest?

This, plus more or less all oil sheer. If you start higher then you'll end up well in the "recommended" weight. Especially in certain engines and extremes of weather.

 

[Hogwash]

This, plus more or less all oil sheer. If you start higher then you'll end up well in the "recommended" weight. Especially in certain engines and extremes of weather.

Are you saying to start with the heavier oil? Of those 2....the M1 appears to be heavier at 100° C