vis index ????
- Thread starter nicholas
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I don't know the actual calculation (outside of a vi calculator) ..but it's the difference of the 40C visc and the 100C visc. The narrower the difference ..the higher the number.
For example ..a mythical oil that would have a 100C visc of 11 and a 40C visc of 12 would have a VI of 982. While an oil with a 100C visc of 11cst and a 40C visc of 150Cst would have a VI of 30
So ..in this case ..from that one dimensional view ..more is better. The hoops that they jump through to achieve the higher numbers is another thing. Synthetic have an advantage here in that they don't need as much doctoring to achieve higher numbers.
Someone with more in tune with give you the stinky on this.
I would think that an MSDS would show specific gravity ..while a product data sheet would show the viscosity index.
For example ..a mythical oil that would have a 100C visc of 11 and a 40C visc of 12 would have a VI of 982. While an oil with a 100C visc of 11cst and a 40C visc of 150Cst would have a VI of 30
So ..in this case ..from that one dimensional view ..more is better. The hoops that they jump through to achieve the higher numbers is another thing. Synthetic have an advantage here in that they don't need as much doctoring to achieve higher numbers.
Someone with more in tune with give you the stinky on this.
I would think that an MSDS would show specific gravity ..while a product data sheet would show the viscosity index.
The viscosity index is the ability of the oil to retain its viscosity (thickness) across a wide temperature range. The better oils have a higher viscosity index. Hope this helps.
Viscosity index is actually the slope of the line when viscosity vs. temperature data points are graphed.
On a product data sheets, the higher the VI index number, the wider the spread between the cold temp rating and the 100C full operating temp viscosity. So 5W oils will have a higher VI than 10W oils.
Some general, approximate VI indexes for conventional oils:
SAE 30 - 105 VI
10W-30 - 135 VI
5w30 - 160 VI
Compare to GC 0w30 with a 176 VI, which is 12 cSt at 100C (a thick 30 weight) and meets the rather difficult 0W spec of 6200 cP at -35C.
Note: Centistokes = Centipoise/specifc gravity
On a product data sheets, the higher the VI index number, the wider the spread between the cold temp rating and the 100C full operating temp viscosity. So 5W oils will have a higher VI than 10W oils.
Some general, approximate VI indexes for conventional oils:
SAE 30 - 105 VI
10W-30 - 135 VI
5w30 - 160 VI
Compare to GC 0w30 with a 176 VI, which is 12 cSt at 100C (a thick 30 weight) and meets the rather difficult 0W spec of 6200 cP at -35C.
Note: Centistokes = Centipoise/specifc gravity
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I don't think that you can stretch it that far, Blue 99.
go here and just plug in the 40C and 100C numbers ..and you will get what the PDS assigns as a VI
go here and just plug in the 40C and 100C numbers ..and you will get what the PDS assigns as a VI
Taken from the bitog glossary
VI (Viscosity Index)
An arbitrary scale used to show the magnitude of viscosity changes in lubricating oils with changes in temperature. Oils with low VI number such as VI=0 ("zero") have high dependence of viscosity change on temperature. They thicken quickly with decreasing temperature, and thin out quickly with increasing temperature. Oils with high VI number such as VI=200, will still thicken with decreasing temperature but not as rapidly, and also will thin out with increasing temperature, but again not as much as low VI oil.
VI number can also be "negative"
Tables found in ASTM Method D 2270 are widely used to determine VI number.
However, VI does not tell the whole story -- it only reflects the viscosity/temperature relationship between temperatures of 40°C and 100°C. Two lubricants or base oils with the same VI number may perform dramatically different at low temperatures in the -5°C to - 50°C range.
VI (Viscosity Index)
An arbitrary scale used to show the magnitude of viscosity changes in lubricating oils with changes in temperature. Oils with low VI number such as VI=0 ("zero") have high dependence of viscosity change on temperature. They thicken quickly with decreasing temperature, and thin out quickly with increasing temperature. Oils with high VI number such as VI=200, will still thicken with decreasing temperature but not as rapidly, and also will thin out with increasing temperature, but again not as much as low VI oil.
VI number can also be "negative"
Tables found in ASTM Method D 2270 are widely used to determine VI number.
However, VI does not tell the whole story -- it only reflects the viscosity/temperature relationship between temperatures of 40°C and 100°C. Two lubricants or base oils with the same VI number may perform dramatically different at low temperatures in the -5°C to - 50°C range.
Gary - I stand corrected in as much as the technical/statistical answer is the slope between the 100C and 40C viscosity data points.
But what I was trying to imply is that in the case of a 5w30 vs. a 10w30, both with identical 100C viscosities of 10.8cSt, the higher VI index for 5w30 is due to being less thick at cold temps than the 10w30.
Higher product data sheet VI translates to better cold temp performance, such as GC at 176 VI and I believe it's the Quaker State Winter Blend at 205 VI.
But what I was trying to imply is that in the case of a 5w30 vs. a 10w30, both with identical 100C viscosities of 10.8cSt, the higher VI index for 5w30 is due to being less thick at cold temps than the 10w30.
Higher product data sheet VI translates to better cold temp performance, such as GC at 176 VI and I believe it's the Quaker State Winter Blend at 205 VI.
I was checking out QS winter blend, and according to their spec sheets the 5w30 has a vis index of 207 !
so this is a good thing ?,
I use this oil in the winter here in ottawa, but would it be a good summer oil as well ?
thanx oil dudes
nik
so this is a good thing ?,
I use this oil in the winter here in ottawa, but would it be a good summer oil as well ?
thanx oil dudes
nik
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Blue ..I somewhat agree ..it doesn't always follow a linear slope ..but generally you're there. I just didn't want a noob to get off on the wrong track (as though I'm ever on the right one)
Note that the 5w30 only thickens to 50Cst ..while most are at 64+/-. The same is true of the 10w30. This shows that the cold properties that affix the "W" rating aren't related too closely with the VI. Otherwise both of these should be various states "beyond" 0W.
QUAKER STATE® WINTER SYNTHETIC BLEND MOTOR OIL
SAE Grade
5w30 10w30
API Service
SL SL
ILSAC
GF-3 GF-3
Specific Gravity @15.6 °C
0.856 0.859
Flash Point, °C
204 208
Pour Point, °C
-45 -35
Viscosity
@ 40°C, cSt
50.0 56.5
@ 100°C, cSt
10.5 10.3
Viscosity Index
207 174
MRV Viscosity, cP (°C)
8,100 (-35) 7,600 (-30)
CCS Viscosity, cP (°C)
3,750 (-30) 3,700 (-25)
Material Number
Bulk
5040736 504811
Note that the 5w30 only thickens to 50Cst ..while most are at 64+/-. The same is true of the 10w30. This shows that the cold properties that affix the "W" rating aren't related too closely with the VI. Otherwise both of these should be various states "beyond" 0W.
QUAKER STATE® WINTER SYNTHETIC BLEND MOTOR OIL
SAE Grade
5w30 10w30
API Service
SL SL
ILSAC
GF-3 GF-3
Specific Gravity @15.6 °C
0.856 0.859
Flash Point, °C
204 208
Pour Point, °C
-45 -35
Viscosity
@ 40°C, cSt
50.0 56.5
@ 100°C, cSt
10.5 10.3
Viscosity Index
207 174
MRV Viscosity, cP (°C)
8,100 (-35) 7,600 (-30)
CCS Viscosity, cP (°C)
3,750 (-30) 3,700 (-25)
Material Number
Bulk
5040736 504811
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