Can 0w20 handle high RPMs

[ekpolk]

Originally Posted by dblshock
take your oci's out 3k, drive like your 80, stay off the I and enjoy the fuel savings on W20.


Nope, I'm going to go 10k miles (I plan to switch from the AFE to Extended Performance), and I will confidently cruise at 85 on the interstate all day long (I guess today, that IS driving like you're 80...) on the hottest summer day -- here in FLORIDA --, and I will lose no sleep over it.

By the way, the Owner's Manual for the 2018 Prius does not even have the heavy use or hot weather recommendation to use a 30 wt oil. It's absolute -- it says use 0w-20 at all times and in all conditions. We are allowed to top off with 5w-20, but are "cautioned" to replace it with 0w-20 at the next change. No other oil viscosities are even mentioned at all, nor are any "extreme" conditions.

 

[PimTac]

Originally Posted by dblshock
ever wonder why they make W30, W40, W50 and W60?




Those grades are available for vehicles that specify those grades. You can run whatever grade of oil you like.

 

[ekpolk]

Originally Posted by dblshock
ever wonder why they make W30, W40, W50 and W60?


No, I don't wonder. I know. It's for engines designed to use the stuff. Engineers may select bigger clearances, or design an engine to run at hotter temps. There's a whole range of reasons why an engine, in its optimized form, may need to use a thicker (or even thinner) oil. BMW does not specify 60 wt oil in some of its engines to satisfy vague worries of owners. It's because they set those engines up for a very different sort of "performance" than that delivered by an Accord or a Prius.

And I can tell you NON-reasons for the making of those oils: they're not made so that owners with vague, ill-founded worries, often rooted in the technology of decades ago, can second guess today's engineers who, among other things, are trying to give us well-performing engines that last far, far longer than those of 20 and 30 years ago.

Will YOU step up and buy me a new engine if I dump 40 wt into my Prius and it fails, and Toyota says, "warranty claim denied, this 40 wt syrup wasn't flowing into the bearings fast enough..."?

 

[Gokhan]

Using the Widman operational viscosity calculator:

PPPP 5W-30 (VI = 170) KV200 = 2.44 cSt
TGMO 0W-20 (VI = 227) KV200 = 2.43 cSt

So, if you use an ultra-high-VI 0W-20, there isn't much difference in viscosity when the oil temperature rises due to high RPM.

 

[Shannow]

Originally Posted by Gokhan
Using the Widman operational viscosity calculator:

PPPP 5W-30 (VI = 170) KV200 = 2.44 cSt
TGMO 0W-20 (VI = 227) KV200 = 2.43 cSt

So, if you use an ultra-high-VI 0W-20, there isn't much difference in viscosity when the oil temperature rises due to high RPM.


Except that engines aren't protected by KV, they are protected by HTHS in oils that have added plastics.

And the uber VI 20s are the worst at that particular point.

 

[dave1251]

Originally Posted by dblshock
take your oci's out 3k, drive like your 80, stay off the I and enjoy the fuel savings on W20.



For once you made no sense with a post. When the oil tempature is not high enough to cause thinning beyond the point to provide adequate protection it does not matter if a 20 or 60 grade is used.

 

[Gokhan]

Originally Posted by Shannow
Originally Posted by Gokhan
Using the Widman operational viscosity calculator:

PPPP 5W-30 (VI = 170) KV200 = 2.44 cSt
TGMO 0W-20 (VI = 227) KV200 = 2.43 cSt

So, if you use an ultra-high-VI 0W-20, there isn't much difference in viscosity when the oil temperature rises due to high RPM.
Except that engines aren't protected by KV, they are protected by HTHS in oils that have added plastics.

And the uber VI 20s are the worst at that particular point.

Strawman argument.

Temporary shear doesn't happen with 100% of the VII. Also, average 5W-30 has more VII than average 0W-20. A_Harman index for TGMO is comparable to that for M1 5W-30.

 

[Shannow]

Originally Posted by Gokhan

Strawman argument.

Temporary shear doesn't happen with 100% of the VII. Also, average 5W-30 has more VII than average 0W-20. A_Harman index for TGMO is comparable to that for M1 5W-30.


Strawman ?

What ?

The fact that you need to know what the high shear viscometry is to see what's likely to happen to the MOFT ???

And please, how is arguing for HTHS a "strawman"...?

 

[Gokhan]

No, I'm saying that HTHSV isn't the critical viscosity. You're making conclusions without actual calculations.

 

[Gokhan]

OK, doing an actual calculation, assuming the A_Harman index is temperature-independent:

M1 0W-20 HTHSV150 = 2.70 cP
M1 0W-20 HTHSV150 = 1.57 cP

M1 5W-30 HTHSV150 = 3.10 cP
M1 5W-30 HTHSV200 = 1.75 cP

So, the HTHSV ratio between 5W-30 and 0W-20 decreases from about 1.15 to 1.11 when the temperature increases from 150 C to 200 C.

Considering that the oil almost thinned by half, does 11% make much difference though? This doesn't even take into account permanent shear. 5W-30 will have more permanent shear than 0W-20. So, it could be almost no difference after including the permanent shear.

I don't think there is whole a lot of difference between a 0W-20 and a 5W-30. If you're really worried about high RPMs, use a 15W-40, 5W-50, 20W-50, or such.

 

[Shannow]

How did you calculate the HTHS 200 ?

i.e. the "actual calculation", please share the methodology

 

[Gokhan]

I just added the note "assuming the A_Harman index is temperature-independent."

 

[Shannow]

Originally Posted by Gokhan
I just added the note "assuming the A_Harman index is temperature-independent."


Note, this is not to be argumentative, I was genuinely exploring what I've been trying to suss out for over a decade now "the HTHS Viscosity Index".

But you can't assume that the Harman Index (properly the ratio of high shear rate viscosity to low shear rate viscosity is constant with temperature)

Data sheets such as this one are ridiculously rare, and I savour them for the completeness
https://bobistheoilguy.com/forums/ubbthreads.php/topics/3307068/Walmart_SuperTech_Synthetic_sp

It's got the High Shear 100C point

Now the papers all show that the temporary shear is greater in higher viscosity oils...e.g. cold oils are thick oils, and stretch the polymers harder than thinner oils do. So you can't assume linearity with temperature.

Given that the difference between MRV and CCS is low shear/high shear, and at those temperatures, 5C halves the viscosity (typically), I've done the math (Pseudo Harman Index" at -30C (sketchy), 100C (as valid as the Hamran Index) and 150C (the Harman Index).

As you can see, the Viscosity Modifiers have a bigger temporary shear (poorer Harman Index) at lower temperatures, as they are pulled apart that much more forcefully.

 

[Shannow]

Originally Posted by Gokhan
No, I'm saying that HTHSV isn't the critical viscosity. You're making conclusions without actual calculations.


All of the industry literature regarding the development of the HTHS concluded that KV with Viscosity Modified oils was misleading with regard to minimum oil film thickness (protection), and adopted the HTHS as the industry standard for the J300 specs....Why did they go to all that trouble if KV was doing the job ?

 

[OilUzer]

My chemist co-worker w/ PhD

always tells me to use high hths at high rpm like towing in the summer heat and car not using higher gears/over-drive ... Never heard him talk about KVxx.

 

[Gokhan]

Originally Posted by Shannow
Originally Posted by Gokhan
No, I'm saying that HTHSV isn't the critical viscosity. You're making conclusions without actual calculations.
All of the industry literature regarding the development of the HTHS concluded that KV with Viscosity Modified oils was misleading with regard to minimum oil film thickness (protection), and adopted the HTHS as the industry standard for the J300 specs....Why did they go to all that trouble if KV was doing the job ?

Saturday-night typo!

I meant "No, I'm not saying that HTHSV isn't the critical viscosity."

 

[Shannow]

Cool...do you follow my spreadsheet ?

I'm still searching for my holy grail, the HTHS Viscosity Index.

 

[Gokhan]

Originally Posted by Shannow
As you can see, the Viscosity Modifiers have a bigger temporary shear (poorer Harman Index) at lower temperatures, as they are pulled apart that much more forcefully.

Good info, thanks. In that case, this works in favor of ultra-high-VI oils like TGMO in terms of HTHSV retention when the temperature rises beyond 150 C though.

 

[ka9mnx]

Originally Posted by Shannow

Except that engines aren't protected by KV, they are protected by HTHS in oils that have added plastics.

And the uber VI 20s are the worst at that particular point.

Exactly why I dislike W20 oils for my vehicles. I'm not comfortable with the HTHS they deliver. The Ranger (back spec'd by Ford) and the F150 (back spec'd by Ford) had terrible results. Both drank the oil like fish and ran noticeably louder with no FE benefits.

 

[dblshock]

...and louder is caused by more friction, simple common sense.