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#3390109 - 06/05/14 08:06 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Shannow]
FetchFar Offline


Registered: 10/17/13
Posts: 831
Loc: Colorado
Originally Posted By: FetchFar
A good choice would be a Stribeck Curve choice of 0.4 on the http://www.stle.org/resources/lubelearn/lubrication/ chart, near minimum friction, yet allows for less viscosity should it occur. ..


The designer would choose the point on the Stribeck Curve FIRST, probably a 0.4 since its just to the right of the friction minimum. ... A second step would be to plug in the desired oil viscosity to use (say a 30), and then to pick a high torque and low rpm case that is worst-case (depends on engine power/torque curves. All that is left is bearing area, something the designer has original control of, a design variable.

Originally Posted By: Shannow
..how do you know what the applied load (pressure) IS for the different geometries and families of engines ?
...and therefore where on the curve that you are when stating that 20s are right ?


The designer already knows the Stribeck Curve point for the particular engine to start with, and he knows the power/torque curves for an engine worst-case, and assume he has also already chosen a 30 oil to get there. Now, a 20 oil has about 10% to 20% less viscosity than a 30, so it actually slides it to the left a bit, but not much as we see on the curve, so we are still hydrodynamic.

Originally Posted By: Shannow
You also need to get the right curve that includes the extensi0n off to the left for friction modified boundary conditions, because as per the paper you linked a few posts back, engines are increasingly operating way off to the left of the chart (which, yes, is logarithmic)
..... As for the left part of the curve, thats in a mixed-boundary lubrication all the way to near-zero, so we almost totally depend on the anti-wear additives to save bearings from destruction there, nothing more can be done, like on start-up in crank/pin bearings, or on cam lobes full time, timing chain pin/links, etc....


Edited by FetchFar (06/05/14 08:07 PM)
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#3390323 - 06/06/14 03:10 AM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
Shannow Offline


Registered: 12/12/02
Posts: 26590
Loc: a prison island
OK...your point is...

Designers know their stuff, and pick a point in the "safe" hydrodynamic range. Designers, knowing your stuff add a safety margin.

So you can install (and advise others) to install a thinner oil.

Problem is, it's not your reading, or analysis of the Streibeck curve (whether it's logarithmic, in pressure units or other), you are simply guessing that it's somewhere, and guessing that changing the oil viscosity moves it somewhere else, and guessing that place is OK.

Except that means that they LOSE their designer installed safety margin, for all of 0.4% improvement in fuel economy (figure 13 of your linked document....and it's a GUESS, pure and simple...not scientific analysis, regardless of the big words.

As to

Originally Posted By: FetchFar
..... As for the left part of the curve, thats in a mixed-boundary lubrication all the way to near-zero, so we almost totally depend on the anti-wear additives to save bearings from destruction there, nothing more can be done, like on start-up in crank/pin bearings, or on cam lobes full time, timing chain pin/links, etc....


With the increases in fuel economy requirements, all of the manufacturers (Honda, Ford, etc.) are telling us that they are operating in boundary mode more and more often, and that the new standards require new and better friction modifiers to provide adequate protection under those conditions...was discussed before here

http://www.infineum.com/sitecollectiondocuments/notebooks/gf5/ResearchReport.pdf

Page 78 or thereabouts.

So if you "guess" that the designers know their job, "guess" that they are all in the hydrodynamic range (probably an incorrect "guess" these days), and "guess" that moving to the left is still in hydrodynamic range, your guesses could be disastrous.

Repeat...modern engines are operating already in mixed mode/boundary for improved fuel efficiency. They are telling us this in their literature, and the test engines that they are electing for their standards.

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#3390475 - 06/06/14 08:49 AM Re: is 0W-20 always better for mpg than 5W-20? [Re: Shannow]
FetchFar Offline


Registered: 10/17/13
Posts: 831
Loc: Colorado
Originally Posted By: Shannow
OK...your point is...Designers know their stuff, and pick a point in the "safe" hydrodynamic range. Designers, knowing your stuff add a safety margin.

Good, we agree on that.

Originally Posted By: Shannow
So you can install (and advise others) to install a thinner oil.

Mostly based on Shell's study at http://priuschat.com/attachments/fuel-efficient-motor-oil-technical-article-pdf.11772/ which I'll quote below.

Originally Posted By: Shannow
Problem is, it's not your reading, or analysis of the Streibeck curve (whether it's logarithmic, in pressure units or other), you are simply guessing that it's somewhere, and guessing that changing the oil viscosity moves it somewhere else, and guessing that place is OK.

You can easily put in 8 cs vs. 10 cs (going from a 20 to a 30 oil) into the ZN/P relationship and shift the curve in http://www.stle.org/resources/lubelearn/lubrication/ .
And yes, any design engineer would place it around 0.4 (maybe upwards of 1). Put 8 cs in instead of 10 cs (again, 20 vs. 30), worst case moves the 0.4 to 0.3 ---> Not much movement on the Stribeck, obviously. The point.

Originally Posted By: Shannow
Except that means that they LOSE their designer installed safety margin,...

The discussion was, in going from a 30 to a 20 weight, and we see that only moves the Stribeck a small amount. Emphasis on SMALL amount. Very little margin lost.


Originally Posted By: FetchFar
..... As for the left part of the curve, thats in a mixed-boundary lubrication all the way to near-zero, so we almost totally depend on the anti-wear additives to save bearings from destruction there, nothing more can be done, like on start-up in crank/pin bearings, or on cam lobes full time, timing chain pin/links, etc....


Originally Posted By: Shannow
With the increases in fuel economy requirements, all of the manufacturers (Honda, Ford, etc.) are telling us that they are operating in boundary mode more and more often, and that the new standards require new and better friction modifiers to provide adequate protection under those conditions...was discussed before here
http://www.infineum.com/sitecollectiondocuments/notebooks/gf5/ResearchReport.pdf
Page 78 or thereabouts.


Thats a pseudo-ZN/P, for the entire engine, for discussion purposes. The ZN/P for the crank journal bearings SPECIFICALLY remain hydrodynamic for running conditions, a very important point to remember. Its well known that the valvetrain, timing chain, rings, operate in mixed-boundary conditions, always have and always will.

Originally Posted By: Shannow
So if you "guess" that the designers know their job......


They do know their job, not a guess. The same people I observed in Mechanical Engineering school & the SAE who did this specific task are sharp people, no doubt.

End of discussion for me. I'll just let the "Improved Fuel Efficiency by Lubricant Design : A Review by R.I. Taylor & R.C. Coy, Shell Research & Technology Centre, Thornton, United Kingdom paper take it from here. Address all questions to Shell from now on please. LOL...
"In our laboratory, it has been observed that in a modern gasoline engine, well designed
automotive bearings can be lubricated with oils as thin as 2.3 mPa.s (and a 20 weight oil has 2.6 to 2.9 mPas) without any observable wear on either con-rod or main bearings.
The assumption that lower viscosity lubricants automatically give rise to thinner oil films in key lubricated contacts in a gasoline engine is also open to question, particularly in the case of piston rings. Laser Induced Fluorescence measurements have found that, in a Nissan gasoline engine, the mid-stroke top ring oil film thickness was greater for an SAE-5W/20 lubricant than it was for an SAE-15W/40 lubricant. "
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#3390689 - 06/06/14 01:05 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
CATERHAM Offline


Registered: 11/18/05
Posts: 9527
Loc: Burlington, Ontario, Canada
Jasper8146, as others have mentioned, your car is spec'd for the 5W-20 grade so in a warranty situation it is possible that you could be questioned as to why you're using a 0W-20.
Now if you're not concerned with that then yes you can use a 0W-20 and even the TGMO 0W-20 as a number of Hyundai/kia owners have with good UOA results. But be advised that TGMO is one of lightest 20 grade oils available so in your climate, since your car is not equipped with oil gauges to monitor things I'd suggest substituting a 1/2-1 quart of M1 0W-40 to give your a somewhat heavier 0W-20 oil. It will still be lighter on start-up than all 5W-20s and even most aftermarket 0W-20s, but it will retain a higher high temp' viscosity.
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#3390781 - 06/06/14 02:57 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
yvon_la Offline


Registered: 05/20/14
Posts: 740
Loc: quebec canada
what does car manufacturer know that we don't?that one is easy,when their car get reviewed they know the reviewer will say how much per year in maintenance the car will cost so the more inexpensive the better ,yep you guessed it some manufacturer went too far a long time ago lol!
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#3390969 - 06/06/14 06:55 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: FetchFar]
Shannow Offline


Registered: 12/12/02
Posts: 26590
Loc: a prison island
Originally Posted By: FetchFar
And yes, any design engineer would place it around 0.4 (maybe upwards of 1). Put 8 cs in instead of 10 cs (again, 20 vs. 30), worst case moves the 0.4 to 0.3 ---> Not much movement on the Stribeck, obviously. The point.


Again, you are stating that you are GUESSING what a designer WOULD do...and using that to make your recommendation that running to the left is still hydrodynamic...you aren't even trying to use science, you are GUESSING what the designer's intent was, and GUESSINg that it will all turn out alright, all of the time.

Originally Posted By: FetchFar
Originally Posted By: Shannow
Except that means that they LOSE their designer installed safety margin,...

The discussion was, in going from a 30 to a 20 weight, and we see that only moves the Stribeck a small amount. Emphasis on SMALL amount. Very little margin lost.


Again, you biring up Streibeck, as 'though it adds validity to your argument, when you are GUESSING at where on said curve it would be...at least others have the honesty to say that the manufacturer's have a margin, and short of overheating/tracking, you won't use it up in "normal use", rather than brigning in a curve that they have no comprehensible idea of where the designers put it...as you say, you could be out bu a factor of 2.5 (0.4 to 1), which if your GUESS is wrong puts it on the wrong side of hydrodynamic

Originally Posted By: FetchFar
The ZN/P for the crank journal bearings SPECIFICALLY remain hydrodynamic for running conditions, a very important point to remember.


Do they ?

that's not what the paper I linked said, nor what Honda say in some of their 16 grade documentation.

You are ASSuming that bearing remain hydrodynamic...in design, I would always make sure that a bearing is hydrodynamic, but my stuff is supposed to run for 200,000 hours, not achieve "adequate" life in a semi disposable appliance,subject to regulators like CAFE


Originally Posted By: FetchFar
End of discussion for me.


Yep, that is always a convincing point


Originally Posted By: FetchFar
I'll just let the "Improved Fuel Efficiency by Lubricant Design : A Review by R.I. Taylor & R.C. Coy, Shell Research & Technology Centre, Thornton, United Kingdom paper take it from here. Address all questions to Shell from now on please. LOL...


I'll bold what I consider to be an important flaw in your guesswork house of cards.

Originally Posted By: FetchFar
"In our laboratory, it has been observed that in a modern gasoline engine, well designed automotive bearings can be lubricated with oils as thin as 2.3 mPa.s (and a 20 weight oil has 2.6 to 2.9 mPas) without any observable wear on either con-rod or main bearings.


I agree with them, however, they are talking about bearings that are designed for the lubricants and operating conditions. They are not saying that 2.3 will protect every engine that's ever been made, which is a common assertion on this site.

They are also not
* GUESSING on a designer's intent
* GUESSING where the designer put the bearing on the Streibeck Curve,
* calculating where the first guess would take them with a change in viscosity
* GUESSing that it will all therefore be OK; then
* making a recommendation on all engines, all designs, based on a card house of guesswork.

Even if the answer is correct (it doesn't fail), the train of thought to get to the conclusion is flawed, and illogical...

illogical UNLESS you KNOW where the bearing in question actually IS on the streibeck curve.

Otherwise "she'll be right" saves space on the message board.

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#3391137 - 06/06/14 10:18 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Shannow]
FetchFar Offline


Registered: 10/17/13
Posts: 831
Loc: Colorado
Originally Posted By: Shannow

illogical UNLESS you KNOW where the bearing in question actually IS on the streibeck curve.


Just spell Stribeck correctly please. LMAO

Not only are the Shell tribologists correct, the entire discussion I clearly layed out explains why Ford for example has easily been able to specify 30-weight oils for their engines in Europe and 20-weight oils in the U.S. for about 10 years now, same engines.

You lose this argument based on the facts and analysis, both.
_________________________
'07 BMW 530xi N52 engine, E60 chassis, 255 hp
'11 Chevy Camaro LS, 3.6L V6, Zeta chassis, 312 hp
'40 Chevrolet Special Deluxe 2-Door Town Sedan

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#3396051 - 06/12/14 08:38 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Clevy]
Geonerd Offline


Registered: 08/05/08
Posts: 653
Loc: Aridzona
Originally Posted By: Clevy
The only difference between those 2 grades will be at start up,and only once the ambient temps get into the negatives,so for your Arizona conditions there will be no meaningful difference so pick a 5w-20 grade in the flavour you like best,or what's on sale and call er done


Exactly.

Here's the key point:

An oil's xW rating describes its viscosity at a very specific, very cold temperature.
The xW rating says NOTHING about the oil's thickness at moderate temperatures.
Depending on where in Arizona the OP is located, this oil may never get colder than 65~70f.
Further, the visc. plot from -35f to 60f is not linear! As the oil is chilled, fractions of the oil will crystallize, causing the visc to rapidly increase at key temperatures. This gives you a stair-step visc/temp plot which is utterly and completely unsuited for calculating 70f visc.

If you want to estimate visc. at Az starting temps, you'd be better off using the oil's VI to extrapolate down from the stated 100C visc.
_________________________
92 Accord Wagon - The White Whale! 225K.
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#3399118 - 06/16/14 04:41 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: CATERHAM]
Jasper8146 Offline


Registered: 04/25/10
Posts: 157
Loc: Lenexa, Kansas
Thanks for the thoughtful response.

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#3399704 - 06/17/14 11:17 AM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
yvon_la Offline


Registered: 05/20/14
Posts: 740
Loc: quebec canada
Usually car maker have have two goal,1 :best bang for $ (to achieve lowest maintenance cost )2 stay to about 10 psi per 1000 rpm(optimal flow/pressure for temperature regulation of oil
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#3399717 - 06/17/14 11:41 AM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
yvon_la Offline


Registered: 05/20/14
Posts: 740
Loc: quebec canada
Also some part maker (allison come to mind)had to create their own rule(exemple:300 hour corrosion test on yellow metal)why?because oil maker tend to always do the minimum required if it isnt spelled in big letter,that is why big rig oil requirement were so thorowly spelled .and it will be even more stringent in 2018 .todays diesel run at 230 f (oil)this means the 212 test is pretty much irelevent for todays trucks.i m sure care will follow
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#3402732 - 06/21/14 04:50 AM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
virginoil Offline


Registered: 09/05/05
Posts: 1023
Loc: western australia
mpg between 5w-20 and 0w-20 is 3/5 x 7/8 x 0 = 0 in this instance.

Are you trying to split hairs ?

Vehicle maintenance such condition of spark plugs and leads, tyre pressure, quality of fuel, air filter condition, traffic route selection, removal of unnecessary weight/parcels in the vehicle is far more important and has greater impact on mpg regardless whether the OEM specifies either a 5w-20 or 0w-20.


Edited by virginoil (06/21/14 04:54 AM)
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#3402736 - 06/21/14 05:02 AM Re: is 0W-20 always better for mpg than 5W-20? [Re: CATERHAM]
virginoil Offline


Registered: 09/05/05
Posts: 1023
Loc: western australia
Originally Posted By: CATERHAM
Jasper8146, as others have mentioned, your car is spec'd for the 5W-20 grade so in a warranty situation it is possible that you could be questioned as to why you're using a 0W-20.
Now if you're not concerned with that then yes you can use a 0W-20 and even the TGMO 0W-20 as a number of Hyundai/kia owners have with good UOA results. But be advised that TGMO is one of lightest 20 grade oils available so in your climate, since your car is not equipped with oil gauges to monitor things I'd suggest substituting a 1/2-1 quart of M1 0W-40 to give your a somewhat heavier 0W-20 oil. It will still be lighter on start-up than all 5W-20s and even most aftermarket 0W-20s, but it will retain a higher high temp' viscosity.


Why not promote the OP to find a ?w-20 oil with the appropriate builder approval. The OEM would quiver how freely it it is touted mix this with that to come up with what ?

Surely with the huge range oil of brands for selection in that grade you have in the USA, compared to OZ, there must be one on the shelf you can add with confidence in an unadulterated form straight out of the container.

Unbelievable from my view point in OZ.


Edited by virginoil (06/21/14 05:07 AM)
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#3402817 - 06/21/14 07:22 AM Re: is 0W-20 always better for mpg than 5W-20? [Re: virginoil]
SHOZ Online   shocked


Registered: 06/28/03
Posts: 1737
Loc: Illinois
I use 0w20 in my '08 Hyundai Accent. 104k miles and runs like a champ. Uses about a 1/2 qt in a 7500 mile OCI. I think the only reason you don't see 0wx oils in the manual is they would have to be synthetic.

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#3403014 - 06/21/14 01:05 PM Re: is 0W-20 always better for mpg than 5W-20? [Re: Jasper8146]
yvon_la Offline


Registered: 05/20/14
Posts: 740
Loc: quebec canada
Could any explain to me why the majority of car maker say to use
5wxx ?how come almost all car maker never say 0wxx .what is wron with a 0wxx oil?is it an issue in the dino version?
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