HTHS vis spec trumps the Kinematic 100C vis spec'

[CATERHAM]

Since the HTHS vis spec' correlates so well with the operating viscosity in an engine at typical operating temps and the KV100 spec' doesn't, the following guide might be useful to judge how thick or thin an oil actually will be in an engine:

HTHS Vis' Value

2.60 cP ...........a light 20wt oil
2.70 cP ...........a mid-grade 20wt oil
2.80 cP ...........a heavy (thick) 20wt oil
2.91 - 3.10 cP ... a light 30wt oil
3.20 - 3.40 cP ... a mid-grade 30wt oil
3.50 - 3.60 cP ... a heavy 30wt oil
3.70 - 3.80 cP ... a light 40wt oil
3.90 - 4.10 cP ... a mid-grade 40wt oil
4.11 - 4.20 cP ... a heavy 40wt oil
4.21 - 4.40 cP ... a light 50wt oil
4.50 - 4.70 cP ... a mid-grade 50wt oil
4.80 - 5.20 cP ... a heavy 50wt oil
5.3 .........cP entry point to a 60wt oil

For any given HTHS vis' you will have a range of possible KV100 values but it is the HTHS vis' that correlates with operating viscosity.

 

[cp3]

Caterham,
So now armed with this information what is the target we are trying to hit regarding oil pressure? I can see that the PP I am currently running generates less oil pressure than GC. What difference will this make to my engine? Would this have any affect on the VVT system? Will the pressure and viscosity difference cause the cam phaser operation?

Definitely makes for another reason to get a Scangauge which can now apparently read oil temp and pressure in a GM application.

 

[subiedriver]

In the winter time, I run Mobil 1 5w-30 HM, as its HTHS is 3.4, which I like. In the summer, I run M1 10w-30 HM, with an HTHS of 3.62. Both are excellent oils, my Subaru seems to like the thick 30 weights.

 

[21Rouge]

Originally Posted By: cp3
Definitely makes for another reason to get a Scangauge which can now apparently read oil temp and pressure in a GM application.


Are you sure cp3? Last year I was considering buying the ScanGauge provided it could state oil pressure and oil temperature for my Chevrolet Traverse and at that time it wasn't possible. Has there been a software or hardware upgrade?

 

[cp3]

There is "new" software but I don't know how new. It is called XGauge I believe and it can read manufacturer specific information as well as the standard OBD2. The GM section lists oil pressure and temperature however it does say it is experimental. For the price if it works it is about the same as getting a good pair of gauges and a mount.

 

[steve20]

this thread needs brought to the top once in a while-




Steve

 

[nooner]

I agree ^^, I learned quite a bit from it, thanks.

 

[martinq]

Mid-may bump!

 

[Jeff_in_VABch]

Oil temperature is one of the most critical engine parameters in a performance engine. NASCAR engines can develop temperatures as high as 245°F at their 700HP level.

A World of Outlaws 410 Sprint engine is the most grueling form of motorsports and these 900HP engines can run oil temps close to 300F.

ASTM D-4683 HTHS testing is at 150C, that’s 302F! You would never, ever see that in any auto or SUV. Most aftermarket oil temperature gauges don’t even read that high. IMO, any oil rating at 150C is just not useful as it is way too far out of the normal or even high operating temp range.

Most of the hot parts of an engine which rely on oil for cooling do not have any lubrication requirement, I.E. the bottom of the piston tops, the valve springs, etc.

While ASTM D-4683 numbers provide additional information about the oil, we are interested about the viscosity on a much lower portion of the curve.

 

[CATERHAM]

You're right, on the street it is not common to see sump oil temp's over 100C (212F) even on the hottest days. particularly here in N/A with our generally low highway speeds.
But on the track some production cars will have their sump oil temp's soar up to 275F-285F or so and one can assume the in bearing oil temp's will be approaching 300F.

 

[BobFout]

HTHS is not about bulk oil temps to begin with...

 

[FZ1]

Sure,boys. I got all that. That's why I run M1 EP 5-20 in my 5-20 spec Accord V6.

 

[CATERHAM]

Originally Posted By: FZ1
Sure,boys. I got all that. That's why I run M1 EP 5-20 in my 5-20 spec Accord V6.

Which is one of the heavier OTC 20wts with a HTHS vis of 2.75cP.

 

[FZ1]

Seriously,though,thanks for your work on this interesting topic. I thought about trying the M1 0-20 and M1 5-20,but noticed that the EP pds showed less ash than the 5-20 and more hths than the 0-20,so at $32 for 5 quarts of Ep and an M1 filter,I'm staying with the EP as one of the several good performing synthetics.

 

[A_Harman]

Originally Posted By: Jeff_in_VABch
ASTM D-4683 HTHS testing is at 150C, that’s 302F! You would never, ever see that in any auto or SUV. Most aftermarket oil temperature gauges don’t even read that high. IMO, any oil rating at 150C is just not useful as it is way too far out of the normal or even high operating temp range.

While ASTM D-4683 numbers provide additional information about the oil, we are interested about the viscosity on a much lower portion of the curve.


I have seen oil temperatures of 286F during track days in my Corvette. This was at Road America in August a number of years ago. So you can't say that you would never, ever see 300F in any auto or SUV. And besides, the actual temperature of the oil in the loaded zone of a bearing will be higher than the bulk oil temperature that is read in the gallery.

Because I do track days, I choose oils that have the best HTHS for a given viscosity grade, as I believe they will give the best protection under extreme conditions. During the winter, I would pick an oil with HTHS closer to the minimum allowance for the viscosity grade.

Engine designers are always designing for the extreme conditions that an engine might see, and it is the minimum HTHS that is specified for a viscosity grade that drives their decisions.

If it is operational viscosity at lower temperatures that you want to know, there are viscosity calculators on the Internet that you can use.

 

[CATERHAM]

Originally Posted By: A_Harman
Originally Posted By: Jeff_in_VABch


Because I do track days, I choose oils that have the best HTHS for a given viscosity grade, as I believe they will give the best protection under extreme conditions.

Since HTHS viscosity is simply an accurate measure of how thick or thin an oil is in an operating IC engine (taken at 150C), a subjective adjective like "best" is not really suitable.
For example, if a HTHS vis' 3.1cP oil provides the optimum oil pressure and therefore the optimum operational viscosity with the oil as hot as it normally gets, running a 3.5cP oil is simply running a heavier oil; it's not "better" it's just heavier.

The main purpose of this thread was to look beyond the largely kinematically based SAE grading system when comparing the operational viscosities of various oils and look to a hard viscosity spec' that can be relied upon for accuracy regardless of the SAE grade on the bottle. HTHS viscosity does that.
Originally Posted By: A_Harman
Originally Posted By: Jeff_in_VABch



If it is operational viscosity at lower temperatures that you want to know, there are viscosity calculators on the Internet that you can use.

You're using the term "operational viscosity" too loosely since it is based on operating engine and oil pressure is the best proxy for operational viscosity which is not kinematically based.
Since viscosity calculators are kinematically based, they do not correlate with operational viscosity very well at all. And even in terms of estimating kinematic viscosities, they are not very useful at temp's much below 0C. They are especially inaccurate when comparing oils with widely different base oil chemistries.
The best way of comparing oils cold start performance down to about 0C is to first look to the HTHS vis' and then the viscosity index. Even though the VI is kinematically based, it is a measure of rate of change.
The lower the HTHS vis the lighter the oil on start-up and the oil with the higher VI with the same HTHS vis will be the lightest on start-up. If the VIs are markedly different, the comparison can still be done but it's not easy.

 

[Jeff_in_VABch]

Have you guys read High Temperature High Shear Oil Viscosity by James A. Spearot? I studied this about 20 years ago when it came out and have not read it lately, but I dont believe you are understanding HTHS. Also, I believe HTHS relates differently to modern engine assemblies and changes in bearing materials and crankshaft finishes in the last 15 or so years.

In the book there are also examples of where an oil with higher HTHS are capable of causing accelerated wear over one with a lower HTHS viscosity depending on the base fillers.

You can read a few pages of it here for free: http://books.google.com/books?id=XjTaOqEgHeEC&printsec=frontcover#v=onepage&q&f=false

Also, this SAE paper is a MUST read to understand current 20W events, but applies to all oil.

http://www.infineum.com/Documents/Crankc...icants-2010.pdf

Look at the tables and figures, they are great stuff. You can also see the HTHS numbers at both 100 & 150C. The bearing wear numbers look counter intuitive at first until you think about the MOFT and bearing clearances.

 

[CATERHAM]

Actually, I made reference to the James Spearot paper in my opening to this thread and again on page 8 by name with a specific quote.

 

[A_Harman]

Originally Posted By: CATERHAM
Since HTHS viscosity is simply an accurate measure of how thick or thin an oil is in an operating IC engine (taken at 150C), a subjective adjective like "best" is not really suitable.
Originally Posted By: A_Harman
If it is operational viscosity at lower temperatures that you want to know, there are viscosity calculators on the Internet that you can use.

You're using the term "operational viscosity" too loosely


I thought you might ding me on these issues.

I lingered over my word choice of "best", but in that context, I thought that it would be logically interpreted as "highest". As far as "optimum oil pressure" is concerned, the owner's manual for my Camaro states that the normal range of safe oil pressure for the LS1 engine is 20-80psi. This I interpret as meaning GM doesn't want to be bothered by people complaining that oil pressure is 2 psi above or below whatever specific value they might quote as being "correct".

I used the term "operational viscosity" in the same context as how it is used on the Widman calculator if Jeff wanted to seek it out on the 'net. Jeff seems knowledgeable enough to possibly have already done this, though.

 

[CATERHAM]

Originally Posted By: A_Harman
Originally Posted By: CATERHAM

Originally Posted By: A_Harman



the owner's manual for my Camaro states that the normal range of safe oil pressure for the LS1 engine is 20-80psi. This I interpret as meaning GM doesn't want to be bothered by people complaining that oil pressure is 2 psi above or below whatever specific value they might quote as being "correct".

I agree with that interpretation of what GM is thinking, but at least they include fully operational oil gauges in the Camero, Corvette and some other high performance offerings.
BMW doesn't bother with gauges at all to avoid the same consumer questions. The attitude is, just use the oil we recommend and enjoy. Hence the use of a variable tach' on models that spec' the Castrol TWS 10W-60; a very strange and unique solution to what is just the possibility of high oil temp's, IMO.