HTHS explanation
- Thread starter petrv
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Does it mean that the difference between values for cold and hot viscosity (5w40, 0w30) is more important, so it means that first I should choose the oil with the minimum difference possible (like your example 0w20) and then I should choose the highest HTHS (which is minor compared to the viscosity difference)?
If I understand it correctly, even if the 0w40 oil has higher HTHS than the 0w20 one, it also contains more VI improvers and other stuff that degrades over time and under high temp and pressure. So the 0w40 can be more shear stable at the beginning, but after some time, all the additives will go away and the 0w20 will finaly stay better? Is this right? If yes, my 5w40 with HTHS=4.51 will be more shear stable than 10w60 with HTHS=5.4 ?
Or will the 0w40 be less shear stable from the beginning? In this case, I don't understad it
Thanks for the explanation. So really, if I understand this right, a low VI would indicate a long term shear stability, while a high HTHS would indicate short term (non-permanent) shear stability?
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Not all high HTHS is due to VIs. Higher quality base oils may have a higher HTHS with less or no VIs and be very shear-stable.
Yes, but generally a higher base oil viscosity is more shear stable than a thin one. In other words, a 15-40 synthetic will be more shear stable than a 0-40 synthetic. It will therefore retain it's HT/HS better. As far as comparing 0-40 to a 10-60...it's a guess...but my money would be on the 10-60 as having more cojones before, during and after use than any 0w-xx.
If comparing the 0-20 to a 0-40...even though the 0-20 may be a better 'thin' oil, it's HT/HS starts off much lower and will continue to be lower (scary). A 0-40 (especially A3) may possible thin more (percentage wise), but will continue to maintain it's HT/HS due to ACEA qualifications for this product and category.
If comparing the 0-20 to a 0-40...even though the 0-20 may be a better 'thin' oil, it's HT/HS starts off much lower and will continue to be lower (scary). A 0-40 (especially A3) may possible thin more (percentage wise), but will continue to maintain it's HT/HS due to ACEA qualifications for this product and category.
First, HTHS is a viscosity measurement, not a shear stability measurement. HTHS is given in units of cP which is dynamic viscosity. Shear stability is usually expressed as a percentage of viscosity loss. You may be able to infer shear stability by looking at the VI and HTHS, or you may not.quote:
Originally posted by petrv:
Does it mean that the difference between values for cold and hot viscosity (5w40, 0w30) is more important, so it means that first I should choose the oil with the minimum difference possible (like your example 0w20) and then I should choose the highest HTHS (which is minor compared to the viscosity difference)?
If I understand it correctly, even if the 0w40 oil has higher HTHS than the 0w20 one, it also contains more VI improvers and other stuff that degrades over time and under high temp and pressure. So the 0w40 can be more shear stable at the beginning, but after some time, all the additives will go away and the 0w20 will finaly stay better? Is this right? If yes, my 5w40 with HTHS=4.51 will be more shear stable than 10w60 with HTHS=5.4 ?
Or will the 0w40 be less shear stable from the beginning? In this case, I don't understad it
So to answer your questions--it depends.
So to summarize it, does it mean that an oil with higher HTHS is more stable under hard conditions (high temp, pressure, etc.)? If there could be a situation that a low HTHS oil will cut it's layer of oil and there is a possibility of metal to metal contact (for example in a bearing) ?
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Rather than looking for an oil with the highest possible HTHS, you should look for an oil that meets and retains the minimum HTHS requirements for your engine.
You may well find an oil with a high HTHS, but that oil may well shear more than another oil with a lower HTHS. A high HTHS number by itself does not guarantee that the HTHS will remain that high.
I see, so I was thinking about it wrong, the HTHS parameter itself doesn't guarantee the quality of oil under hard conditions. So what parameter should I look for in datasheets? You wrote that there are oils with lower HTHS but better lower shear - how to find them?
To Slick nailed it right on the head
And my friends here is what that ratio is for some of the oils I used in my ride:
Mobil 1 0W-40 * GC 0w30 * Mobil 1 0w30 * Mobil 1 5w30 * Mobil 1 10w30 * Mobil 1 0W-20 * Red Line 5W-20
1.69 * 1.43 * 1.50 * 1.40 * 1.31 * 1.43 * 1.17
However I found(based on UOA) that Mobil 1 0W-40 gave me best protection(but this might be due to the Auto RX cleaning before that OCI and use of LC during the OCI) and lowest wear rates, followed by GC and Mobil 1 10w30. Mobil 1 0W-20 was by far worst...
Here are the wear rates ppm per 1000 miles:
Mobil 1 10w30/GC 0W-30/Mobil 1 0W-20/Mobil 1 0W-40
ALUM 0.75/0.57/0.8/0.43
CHRO 0.11/0.11/0.2/0.14
IRON 2.58/2.39/2.4/1.43
COPP 0.86/0.57/1.0/0.71
LEAD 1.40/1.36/2.2/1.29
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