Which is more important? HT/HS or VS@100C

[04SVT]

Like the title says. The reason I ask is; I've been going over the tech data sheets for the following oils. While all seem really good and similar; there are differences. While one oil may have better viscosity at 100 degree celcius another oil will have better HT/HS numbers. It should be noted that the car is driven to the extreme almost everyday at some point. Not for long periods though. Also, the engine routinely operates at 100c regularly since ambient temp is quite often at or just below 40c here in Texas.

 

[d00df00d]

HTHS for sure.

The most important parts of your engine are high-shear, and run at temps that are much higher than the oil's average temp. HTHS is a MUCH more useful indication of how the oil will act in those conditions.

 

[ARCOgraphite]

Its an invalid question, but if you are concerned and drive hard dont use ILSAC oils in 30 grade as they will limit the HTHS to a low value to show(required for RC) good fuel economy. You have to look at Racing or Diesel oil or ACEA A3/B4 to have the high(er) hths.
To answer your question, HTHS is the "oil stock tuffness spec" and is the most critical in HDEO and HD applications over kv100(boiling pt viscosity). If Automakers are trying to show good cafe numbers the Low viscosity and attendant low HTHS and readily sheared and recombined VII are whats critical - opposite of what a hard driver wants.

 

[martinq]

HTHS hands down. If I could know only one spec on an oil this would be top on the list.

 

[daman]

HTHS here.

 

[Turk]

Originally Posted By: 04SVT
I've been going over the tech data sheets for the following oils.



Which oils??

 

[04SVT]

Ok, well I was looking at the following oils and their specs. The Moutl has the highes VS@100c but is slightly lower hths than the RL. How much of a difference is there between 3.5 and 3.8 hths. Heck, how much of a difference is there between 3.0 hths (the lowest) and 3.8 hths (the highest)?

Motul
http://www.motul.com/system/product_descriptions/technical_data_sheets/51784/300V_Power_Racing_5W-30_(GB).pdf?1339171623

Redline
http://www.redlineoil.com/product.aspx?pid=2&pcid=21

Amsoil
http://www.amsoil.com/storefront/asl.aspx

M1 EP
http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil_1_Extended_Performance.aspx

PU
http://www.pennzoil.com/wp-content/uploads/2012/02/PENNZOILULTRAFullSyntheticMotorOil.pdf

 

[Turk]

Edit: You're PU is the SM one... Here is the SN version: http://www.epc.shell.com/Docs/GPCDOC_X_cbe_24855_key_140007304054_201207271344.pdf

I was just looking some of those up...

PU 5w-30 = 3.1
ASL 5w-30 = 3.2
AZO 0w-30 = 3.1
HDD 5w-30 = 3.5

 

[gtoracer]

where is Cat when u need him.

 

[ARCOgraphite]

You won't know when HTHS is too much until you try it and it feels like your pulling a Airstream. No need to go over 3.5 with a healthy engine spec'd for ILSAC lubes. Eurospec ACEA A3 5w30 or 10w30 will be what you want above freezing.

 

[LeakySeals]

So by this number Red Line is best for hot temps, and the M1 taxi cab Las Vegas desert commercials are nothing but a mirage?

 

[Gabe]

You are comparing racing oils to extended drain oils - two different types of oils for two different purposes.

I agree with ARCO on looking for the ACEA A3 spec.

 

[dparm]

HTHS is "more" important but you should really look at how the oil performs as a whole.

 

[friendly_jacek]

More important for what?

Are we talking fuel efficiency or wear protection? What is the engine requirement?

 

[04SVT]

Originally Posted By: friendly_jacek
More important for what?

Are we talking fuel efficiency or wear protection? What is the engine requirement?


Engine wear for sure. I can't imagine picking an engine oil for fuel mileage. The car is drag raced regularly. Sees red line (7000 rpm) all the time.

 

[04SVT]

Originally Posted By: dparm
HTHS is "more" important but you should really look at how the oil performs as a whole.


What else in the tech specs is an indicator of performance?

 

[dparm]

Originally Posted By: 04SVT
Originally Posted By: dparm
HTHS is "more" important but you should really look at how the oil performs as a whole.


What else in the tech specs is an indicator of performance?


Arguably the HTHS divided by the dynamic viscosity @ 150C shows shear resistance (you'll have to calculate that). Also, some say that a low NOACK value indicates high-quality basestocks.

But really the spec sheet can't tell you everything. Best way to judge its performance is to try it out and get the oil analyzed.

 

[CATERHAM]

HTHSV trumps the KV100 spec'.

If you know the HTHSV of an oil you can ignore the KV100 spec'.
The reason is because the kinematic measure doesn't take into consideration the viscosity-pressure coefficients of different oil chemistries.
Even though the HTHSV is usually provided at 150C, the viscosity change with temperature is virtually linear from 150C down to 100C and to even lower temp's with light oil grades.
The other viscosity factor that one must take into consideration is the viscosity index of an oil.

For example, if two oils have the same HTHSV and the same VI's they will have the same operational viscosities at all temp's down to at least 0C regardless of what their respective KV100 spec's are.

The subject was discussed in detail in the following thread:

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2276634&page=1

This question comes up a lot. I think the above thread should be posted on the BITOG Home page in the Additional Reading column, with the simple title "HTHS viscosity trump's the Kinematic 100C spec'".


The subject was discussed in detail

 

[04SVT]

Originally Posted By: CATERHAM
HTHSV trumps the KV100 spec'.

If you know the HTHSV of an oil you can ignore the KV100 spec'.
The reason is because the kinematic measure doesn't take into consideration the viscosity-pressure coefficients of different oil chemistries.
Even though the HTHSV is usually provided at 150C, the viscosity change with temperature is virtually linear from 150C down to 100C and to even lower temp's with light oil grades.
The other viscosity factor that one must take into consideration is the viscosity index of an oil.

For example, if two oils have the same HTHSV and the same VI's they will have the same operational viscosities at all temp's down to at least 0C regardless of what their respective KV100 spec's are.

The subject was discussed in detail in the following thread:

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2276634&page=1

This question comes up a lot. I think the above thread should be posted on the BITOG Home page in the Additional Reading column, with the simple title "HTHS viscosity trump's the Kinematic 100C spec'".


The subject was discussed in detail



Thank you for taking the time to repost for me. I will read it now. Sorry as well for asking a redundant question.

 

[04SVT]

Originally Posted By: tpitcher
Edit: You're PU is the SM one... Here is the SN version: http://www.epc.shell.com/Docs/GPCDOC_X_cbe_24855_key_140007304054_201207271344.pdf

I was just looking some of those up...

PU 5w-30 = 3.1
ASL 5w-30 = 3.2
AZO 0w-30 = 3.1
HDD 5w-30 = 3.5



Which PU is what they have on the shelf at Walmart? SM or SN? I also don't know what ASL, AZO, or HDD oils are. I looked on the acronym thread.