xW-HTHS grade selection

Status
Not open for further replies.
Joined
Aug 1, 2017
Messages
2,909
Location
WA
let's say I'm looking for 5 or a 0x3.6 +/- in either 30 or 40 grade.
Is it better to get a 0Wx30 or a 0Wx40 with a comparable hths?

I'm aware of 40 having more VII (VM).
Would the moft be the same since both have similar hths? I forget what role KV00 plays in that. Obviously 40 has higher KV100.
also know that x40 may increase the fuel cost very? slightly.

Any other pros and cons? Which one would you select if they both met your engine's spec?
Basically high hths x30 vs. low(er) hths x40.
 
Mate, my preference for oils here in OZ (when I had vehicles without DPF, lest the troll emerges) was Edge 5W30 A3/B4.

Could run it in anything that I had.

Now I'm in C3/Dexos 2 category, I'm faced (mostly) with 5W40s

xW-HTHS....that's how i should be.

When you read some of the literature about the Japanes uber high VI 0W20s, they were hamstrung with J300 being initially based around KV100 (HTHS is a VERY late addition) but wanting better economy, so went light on basestocks, and high in VII...J300 drove a certain behaviour.

xW-HTHS, we wouldn't be talking about the KV100 (30, 40, 50 grade), but a cold weather parameter and a bearing protection parameter.

It would negate the need to produce both (say) 5W30 and 5W40 3.5/3.6 HTHS oil, with the 40, in my opinion being the inferior for a given HTHS.
 
Shannow,
btw, first time I read about the idea of xW-HTHS was in one of your posts.
I like it better than the current system. I get a better idea with hths than a 30 or 40 ...
 
9 out of 10 times an oil with a higher KV100 will typically have the higher HTHS. That's what I saw when comparing many diffetent oil choices.
 
Originally Posted by OilUzer
let's say I'm looking for 5 or a 0x3.6 +/- in either 30 or 40 grade.
Is it better to get a 0Wx30 or a 0Wx40 with a comparable hths?

I'm aware of 40 having more VII (VM).
Would the moft be the same since both have similar hths? I forget what role KV00 plays in that. Obviously 40 has higher KV100.
also know that x40 may increase the fuel cost very? slightly.

Any other pros and cons? Which one would you select if they both met your engine's spec?
Basically high hths x30 vs. low(er) hths x40.


Fuel economy pretty much tracks with HTHS, so if you can find a 30 and a 40 with the same HTHS, the fuel economy will be pretty much the same.
Since you're talking only about 0w30 or 0w40, the viscosity indexes will be pretty high for both. Maybe a higher VI oil would give better fuel economy if you do a lot of short trips, and the oil never gets up to operating temperature.

Something else to think about would be long-term shear viscosity loss. Say if you can find a 0w40 with 3.6 HTHS, and a Temporary Shear Ratio (TSR) of .84, and a 0w30 with 3.5 HTHS, and a TSR of .90. Data on long-term shear is rare to see on BITOG, but the small amount that I have seen indicates viscosity loss is about half the difference between 1.0 and the TSR . So the 0w40 would lose about 8% (1.0-.84=.16, half of .16 is .08, or 8%) of its virgin HTHS of 3.6, ending up at 3.31. The 0w30 would lose about 5% of 3.5, ending up at 3.33. So after long-term shear has taken its cut, the two would have comparable HTHS.
 
OilUzer, I am really glad you asked this; I have been wondering the same thing for awhile now too.
On the topic of picking an oil with HTHS at or above 3.5, we can grab something A3/B4 rated, but if not then just API SN 10w-40, 20w50, HDEO 15w40, HDEO 5w-40.
Since my OCI is fairly short (personal decision after approached with fuel dilution), I get caught looking at these grades, and the back of my head says "should I care about the KV100 at all..?"

When picking between blends with the same HTHS and same group basestock, I have generally viewed high KV100s as something undesireable because I figure those with higher KV100 have more VM.
 
Personally a combination factor of cost and manufacturer approvals trump the small differences betweeen a 0w30 and 0w40 both having a HTHS close to, but no less than 3.5.

I have a hunch the difference in blend and additive packs will be more significant to the oil performance than marginal differences in HTHS.
 
Originally Posted by OilUzer
let's say I'm looking for 5 or a 0x3.6 +/- in either 30 or 40 grade.
Is it better to get a 0Wx30 or a 0Wx40 with a comparable hths?

I'm aware of 40 having more VII (VM).
Would the moft be the same since both have similar hths? I forget what role KV00 plays in that. Obviously 40 has higher KV100.
also know that x40 may increase the fuel cost very? slightly.

Any other pros and cons? Which one would you select if they both met your engine's spec?
Basically high hths x30 vs. low(er) hths x40.





I was faced with a similar situation with the oil for my Corvette. The new Mobil 1 ESP Formula 0w40 vs the ESP Formula 5w30, only in this case the 5w30 actually has a higher HTHS of 3.58 vs 3.53 for the 0w40. So I chose the 5w30 (although the choice was pretty much made for me already since the 0w40 is difficult to find but the 5w30 was available at Canadian Tire)

I'm pretty confident that the 0w40 will have more VII in it than the 5w30, so I think in the long run having an oil with less VII will keep the engine much cleaner. (plus it should hold it's viscosity and HTHS better as well)
 
Before I post the question, I was leaning towards x30 mainly due to lower vii but wasn't sure at all. A bad analogy was in my head. right or wrong, I always preferred a small v6 over a big 4 cylinder in the good old MPFI days. So was thinking maybe x40 (more horses/moft) over x30 but stand corrected.

Thank you all.
 
Last edited:
Threads like this follow my line of thinking that HTHS is more important than kinematic viscosity. Is there any circumstance in an engine where kinematic viscosity plays an important role? (like drain from the head(s) to the pan)
 
Originally Posted by RDY4WAR
Threads like this follow my line of thinking that HTHS is more important than kinematic viscosity. Is there any circumstance in an engine where kinematic viscosity plays an important role? (like drain from the head(s) to the pan)


is there any relationship between KV and hths at all? For example can you make x30 with hths of 4.3 or higher if ACEA? or other specs didn't impose a limit on it?
What's the highest hths that is possible with x30 before the need to move up to x40 or higher?
 
Last edited:
Originally Posted by OilUzer
Originally Posted by RDY4WAR
Threads like this follow my line of thinking that HTHS is more important than kinematic viscosity. Is there any circumstance in an engine where kinematic viscosity plays an important role? (like drain from the head(s) to the pan)


is there any relationship between KV and hths at all? For example can you make x30 with hths of 4.3 or higher if ACEA? or other specs didn't impose a limit on it?
What's the highest hths that is possible with x30 before the need to move up to x40 or higher?


Will do some messing on that topic...

Firstly, I don't think that you can get into the 4s with something that meets SAE 30.

Will start with Citgo monogrades, as they have good data sheets
http://www.docs.citgo.com/msds_pi/10004a.pdf

You can see that the "natural" HTHS for a 30, on the thick end is 3.5-3.6.

You can only go up to 12.5 KV100, so not a lot of room to play with...start with the 30, at 91%, and the 50 at 9%...KV100 is 12.48.
Corresponding HTHS would be 3.7...so that's probably about as far as it can be stretched.

A High VI PAO might get another point or so...
 
Was just doing some search and found an old post By Shannow. If I'm not mistaken he was saying that with a newtonian fluid (e.g. straight weight oil), hths is equal to kv150. Hopefully I'm not taking it out of context ...

Not sure about multi viscosity oil. It wasn't discussed directly and it's a long thread ...

Edit:
Shannow,
I didn't see your post when I was posting this.
 
Last edited:
Originally Posted by OilUzer
Was just doing some search and found an old post By Shannow. If I'm not mistaken he was saying that with a newtonian fluid (e.g. straight weight oil), hths is equal to kv150. Hopefully I'm not taking it out of context ...


Not quite...HTHS is dynamic viscosity, KV150 is kinematic.

The difference between the two is density at the test temperature...kinematic viscosity is like flow through a tube, under the weight of the oil above it, while dynamic is the viscosity between the two rollers.

Take the Citgo 30, the KV100 is 12.0Cst...the Dynamic viscosity would be 9.97 (essentially 10) at 100C.

Using the Widman calculator, the KV150 would be 4.49
Using the density calculator, the density would be 0.791
The dynamic viscosity calculates out to 4.49*.791 = 3.55 (3.6)

and the HTHS is 3.6.

For a newtonian fluid there is no change in viscosity with higher shear rates, wheres at around 10^5 to 10^6, polymeric thickened oils lose viscosity and reach a "second newtonian" plateau.

The "Harman Index" looks at the behaviours above...the Newtonian dynamic viscosity versus the HTHS....mongrades, it is the same.



resources
https://www.widman.biz/English/Calculators/Operational.html
https://planetcalc.com/2834/
https://www.convert-me.com/en/convert/density/lbpgal.html?u=lbpgal&v=7.4
 
Oil Pressure vs KV100 vs HTHS plots of various oil brands and viscosity. Oil Pressure is very linear to HTHS as mentioned earlier.

KV100 vs HTHS.JPG


OP vs KV100 vs HTHS.JPG
 
Status
Not open for further replies.
Back
Top