HT/HS formula

[priler]

assuming you have other specs on an oil,what is the calculation or formula to get the ht/hs?

i'm thinking you need the KV and density at least and possibly more,but what is the math to get ht/hs?

i was talking to someone about there oil and the ht/hs value they give for it,and found out it's actually a calculation they did.

i realize that the best way to know is the proper testing,like ASTM D4741,but without this information being put forward,maybe the calculation can give a fairly accurate value.

also,would the type of base stock askew the calculation?(like a grp 3 compared to 4/5,etc.,etc.)

 

[Gary Allan]

AFAIK the HT/HS number is done via a mechanical test. One is the tapered plug test ..which IS the ASTM D4741 protocol. I imagine that one "can" calculate it to some reasonably accuracy ..but it's not validated without the test. The cost of the test is beyond hobby grade pricing. I think the best price I got was $250.

 

[glxpassat]

You may be able to calculate it for the base oil since it doesn't shear, knowing a few data points. But if viscosity index improvers are added, I think that would complicate things as some improvers are more shear stable than others.

 

[Gary Allan]

I'm sure that secondary blenders (those that aren't producers of base stocks) have software to factor a HT/HS with a given blend. The producers provide the data. Most oils are "packages" that are licensed by the original formulator. I also think, above a given minimum (somewhere between 2.6-3.0), that it's not all that much of an issue for all but the extreme crowd.

 

[priler]

yes,thank you.the info in both post are known to me,but i believe there is still a calculation that can be used.


....not necessarily for exactness in all oils,but if i can verify that the formula works in a specific oil for which most or all perameters are known,then i can use it fairly accurately in other oils and adjust for several differences.this would be particularly useful if the info is not forthcoming and to confirm.

 

[Gary Allan]

HT/HS typically follows viscosity. You'll find some throw in their magic potions to "enable" higher than typical numbers ..so that would be a hard point to mathematically factor.


Read from left to right 0w-20/5w-20/5w30/10w-30 (PP)

HT/HS Viscosity, cP ASTM D-4683 2.6 2.6 3.1 3.15

Read from left to right 15w40/10w-30 (Pennzoil Long Life)

HT/HS Viscosity, cP ASTM D-4683 4.3 3.5