Optimal kinematic viscosity for mimimal wear?

[friendly_jacek]

Originally Posted By: Gary Allan
I wanted to touch back here for a bit.

Quote:
Wear at 50°C was extremely small due to significant reduction in the severity of contacts due to the increased film thickness resulting from increased oil viscosity. The wear rate under this condition was near zero. However, the wear rate increased when the oil temperature was raised to 100°C again.

Also, the friction torque decreased with increased speed at 100°C because the valvetrain operates in the mixed or EHD lubrication regime. However, at 50°C the friction torque variation with speed became flatter compared to that observed at 100°C. This is due to fewer mechanical interactions between asperities on two sliding surfaces due to increased oil viscosity.


This is exactly the opposite on the Schneider Cylinder/Ring wear paper. In that study, wear was highest when the engine was cold and evaporated as the engine warmed (visc obviously being lower). This is 180° out of that wear relationship.


Gary, I guess you did not read the methods carefully. The 1ZZ-FE paper studied radiotraced rings in a fired engine. The other paper used a motored valvetrain rig. As I pointed previously, the start up wear in ring/bore is mostly chemical/corrosive and that was observed indeed in the rings of fired engine. The valvetrain setup was free of combustion blow back and showed less friction and less wear with thicker oil as it can be expected in hydrodynamic lubrication (thick oil) vs boundary lubrication (thin oil).

So no, there are no discrepancies and engine wear is more complex that the usual thin/thick dispute.

 

[Gary Allan]

Quote:
As I pointed previously, the start up wear in ring/bore is mostly chemical/corrosive and that was observed indeed in the rings of fired engine.


Well..you asserted that it's so ..and I even recall reading about it ..but I didn't see you establish that it's the overwhelming major contributor to the startup (Castrol's infamous 90% marketing hype) wear scenario.

..or did I miss that reference somewhere?

I have a hard time buying a 20 minute duration (naturally on a curve) for such a corrosive event.

 

[friendly_jacek]

Originally Posted By: Gary Allan
Help me with my CliffNotes scanning. Just what viscosity were they testing at?

Are you doubling your wear rate since you're not using 50 or 60 weight oil? If yes, is that wear rate significant? If no, why not since you're at a lower viscosity?

The title of the paper is

Valvetrain Friction and Wear Performance with Fresh and Used Low Phosphorous Engine Oils

..and appears to be proving that lowering additive levels increases wear.


Poor reading comprehension.

1. The authors did not compare 20 weight to 50-60 weight.
2. The authors did not define what wear is significant.
3. The authors did not prove that lowering additives increases wear.

What authors did prove is that used oil decreased friction (10%) and wear (order of magnitude) independent from increase in viscosity (oxidation) or decrease in ZDDP levels.

The reason I referenced that paper is that authors' data nicely illustrated that dogma of tribology that thicker oils provide for thicker oil films and lowest wear compared to boundary lubrication with lesser viscosity oils.

And again, the OP's question was "Optimal kinematic viscosity for mimimal wear?" He did not ask about optimal balance between wear and fuel efficiency.

 

[friendly_jacek]

Originally Posted By: Gary Allan


..or did I miss that reference somewhere?

Quote:

Fig.20 shows the results of ring wear measurements by
varying the inlet cooling temperature. The lower the
coolant temperature, the greater the wear. This tendency
become more pronounced when the coolant temperature
is 40 degree celsius and below. Furthermore, even in the
case of high-sulfur fuel, ring wear is small when the water
temperature is 80 degree celsius and above. As can be
seen in Fig.17, change in coolant temperature manifests
the change in wear rather quickly.

This mechanism is as follows:

• Acids in the bore increase when coolant temperature
is low.
• The acids eliminate oil film between the bore and
piston rings.
• Abrasive wear between the bore and piston rings
increase.


http://hosting.dynamis.net/littlerocket/MMCAllAluminumCylinderBlock(2ZZ-GE).pdf

 

[Gary Allan]

Quote:
Poor reading comprehension. 1. The authors did not compare 20 weight to 50-60 weight.


I'll say. Reread it. I wasn't even referring to the text when I offered the statement. I was offering to OVERKILL (or was it BGN?) that since there were greater viscosity fluid than they were using ..that they too much be experiencing more wear as it warms since it transitions from a higher viscosity to a lower one.

Pretty straight forward if you ask me.

 

[Gary Allan]

Fig.20 shows the results of ring wear measurements by
varying the inlet cooling temperature. The lower the
coolant temperature, the greater the wear. This tendency
become more pronounced when the coolant temperature
is 40 degree celsius and below. Furthermore, even in the
case of high-sulfur fuel, ring wear is small when the water
temperature is 80 degree celsius and above. As can be
seen in Fig.17, change in coolant temperature manifests
the change in wear rather quickly.

This mechanism is as follows:

• Acids in the bore increase when coolant temperature
is low.
• The acids eliminate oil film between the bore and
piston rings.
• Abrasive wear between the bore and piston rings
increase.

..and this somehow accounts for the entire 20 minute elevated wear event ..even with 100C coolant temps withing 4-5 minutes of operations?

I see. Clearly this is true.

So, Schneider was FOS? NO such 20 minute wear curve existed? His pals in the peer review committee just liked him?

 

[FZ1]

So,then,thinner oil would allow the coolant to reach operating temperature more quickly thus reducing wear on start up where most wear is said to occur. I love it when Thin Wins!

 

[friendly_jacek]

Originally Posted By: Gary Allan


So, Schneider was FOS? NO such 20 minute wear curve existed? His pals in the peer review committee just liked him?


I did not see his poster presentation, but the 15-20 minutes increased wear is totally consistent with oil wash down from fuel on start an then corrosive combustion etching that in turn produces more wear due to uneven surface.

I did read his another (newer) abstract: http://www.sae.org/technical/papers/2006-01-3413

The interesting result is this:

Quote:

This work examines the effects of lubricant properties on wear rates of the ring/bore interface. Results show that engine oil service classification, the level of antiwear additives, severe engine aging, synthetic formulations, and viscosity classification have little or no impact on wear rates.


So, now we know that the thin oil protection on start up is a myth (so much for Dr Hass's hypothesis and his eloquent writing).

Also, if the wear is not related to oil type or viscosity, then maybe there is NO oil at rings during start and instead we are dealing with corrosion indeed (as I showed previously)?

 

[Peted]

Originally Posted By: FZ1
So,then,thinner oil would allow the coolant to reach operating temperature more quickly thus reducing wear on start up where most wear is said to occur. I love it when Thin Wins!


Did you not read Anything in this thread?

 

[FZ1]

Did you?

 

[Gary Allan]

Originally Posted By: friendly_jacek
Originally Posted By: Gary Allan


So, Schneider was FOS? NO such 20 minute wear curve existed? His pals in the peer review committee just liked him?


I did not see his poster presentation, but the 15-20 minutes increased wear is totally consistent with oil wash down from fuel on start an then corrosive combustion etching that in turn produces more wear due to uneven surface.


I have a very hard time buying that fuel wash down is a factor much beyond (at the outside stretch) the end of fuel enrichment ..which is a brief period out of the 20 minute curve to steady state.

Quote:


I did read his another (newer) abstract: http://www.sae.org/technical/papers/2006-01-3413

The interesting result is this:

Quote:

This work examines the effects of lubricant properties on wear rates of the ring/bore interface. Results show that engine oil service classification, the level of antiwear additives, severe engine aging, synthetic formulations, and viscosity classification have little or no impact on wear rates.


So, now we know that the thin oil protection on start up is a myth (so much for Dr Hass's hypothesis and his eloquent writing).

I have not ever subscribed to thinner oil providing more protection at start up (warm up). I've leaned much more toward ill fitment of parts and additive process temps being the cause of the accelerated wear retreating HAND IN HAND with increases in oil temp ..which is the indication of thermal saturation. Schneider didn't either. He only correlated cylinder/ring wear to the 20 minute oil warming event ..at least that's what I saw when I bought a copy of it.

Quote:

Also, if the wear is not related to oil type or viscosity, then maybe there is NO oil at rings during start and instead we are dealing with corrosion indeed (as I showed previously)?




I still don't see the "showed" part of it. I see you assigning it merit where their may be little.

You have to watch the "maybe's" ...the next evolution is "as I clearly demonstrated"

SAE publications usually have an agenda. When thin oils are envogue, you will see studies showing the benefits of light oils. When OEMs want to prove that their fluids are better than alternatives, those studies will surely ..by gosh..prove it to be so.

You have to look at what the study set out to prove. It always succeeds.

I'd love to see the study that 100% fails to meet its intended goal.

I see many who are men of faith here. They're cherry picking from scripture through all the chapters and verses.

 

[BuickGN]

Originally Posted By: FZ1
So,then,thinner oil would allow the coolant to reach operating temperature more quickly thus reducing wear on start up where most wear is said to occur. I love it when Thin Wins!


You shouldn't post when drunk.

 

[FZ1]

So should you? The point is, the more quickly the engine (coolant)warms:The more quickly the wear decreases,right?? Thin oil allows the engine to warm more quickly than thick oil,right?? Think really hard.

 

[BuickGN]

Originally Posted By: FZ1
So should you? The point is, the more quickly the engine (coolant)warms:The more quickly the wear decreases,right?? Thin oil allows the engine to warm more quickly than thick oil,right?? Think really hard.


How did you ever arrive at that conclusion?? Please, I'm curious how thin oil allows the engine to heat up quicker. You can't have it both ways. In one thread you guys say thin makes the engine run cooler and in another thread you say it makes the engine heat up quicker. Pick one.

This is getting comical.

 

[ekpolk]

Originally Posted By: friendly_jacek
. . .
I did read his another (newer) abstract: http://www.sae.org/technical/papers/2006-01-3413

The interesting result is this:

Quote:

This work examines the effects of lubricant properties on wear rates of the ring/bore interface. Results show that engine oil service classification, the level of antiwear additives, severe engine aging, synthetic formulations, and viscosity classification have little or no impact on wear rates.


So, now we know that the thin oil protection on start up is a myth (so much for Dr Hass's hypothesis and his eloquent writing).

Also, if the wear is not related to oil type or viscosity, then maybe there is NO oil at rings during start and instead we are dealing with corrosion indeed (as I showed previously)?



FJ: Careful there, you're putting yourself waaaaaay out there on the limb.

First, you read an abstract. Not the paper. And you leap from that all the way to "now we know that the thin oil protection on start up is a myth. . .". And to bolster your credibility, you add a totally unnecessary ad hominem attack on Dr. Haas. A mere abstract gives you nothing remotely close to a "now we know". The abstract doesn't even mention startup wear as distinct from other wear.

Which leads to, second, you really need to bone up on statistics and scientific method. Scientists and engineers write papers all the time. Some are very predictable and uncontroversial. Others push boundaries that have never been explored before. But it is a rare study-paper combo that leads everyone to exclaim "eureka, now we know..." without any qualifiers or caveats. It just doesn't work that way. Or turn it around and consider it this way: are you suggesting that since "now we know...", all those scientists and engineers can just close up shop and go look for other jobs? And since you pulled Dr. Haas in, I'll mention that it's clear from both his writing and commentary here (totally apart from his content), that he is vastly more familiar with stats and scientific method than you are.

It usually takes years, the work of many different scientists and engineers, and much statistical analysis before anyone can unilaterally declare, "now we know..." anything of any degree of complexity.

 

[FZ1]

Thin oil rises in temperature more quickly than thick oil. I've got an idea for you; Just bring me the facts and I'll tell you what they mean. I'm a big picture kind of guy.

 

[BuickGN]

Originally Posted By: FZ1
Thin oil rises in temperature more quickly than thick oil. I've got an idea for you; Just bring me the facts and I'll tell you what they mean. I'm a big picture kind of guy.


You're so far off even the thin oil guys are not going to agree with you. You really need to research more before posting.

I'll explain it for you. Thin oil does not heat up faster. Thin oil is thinner during the warm up process. Both thick and thin will arrive at full temp at the same time. Thin will hit the thick oil's 100c viscosity first. This is like questioning if the world is round. You're just making yourself look bad. You can't see the big picture if you can't see an inch in front of your face.

 

[SuperBusa]

Originally Posted By: zoomzoom
Quote:
It's all about temperature. That's why it's gets very misleading to talk about any SAE grade of oil without that temperature context. If you're talking kinematic viscosity you've largely eliminated the temperature component from the the discussion. I love to tell my friends I'm using a 0W-20 oil at the track for the shock effect. The reality is I'm running a 9 cSt oil. And on the street typically a 17 cSt oil.


my point exactly, you nailed it!


Some related info.

http://www.audiworld.com/tech/eng14.shtml

 

[FZ1]

It would seem that the thinner substance would warm more quickly than the thicker substance. If not; why not?

 

[Bryanccfshr]

No, the thicker substance will produce more friction as it is pumped and as it circuits(frction is the defines viscosity) friction=heat/
This does not mean optimal viscosity is reeached quicker with thicker oil, it just meanns the oil heats up faster bscause it is creating its own heat by being pumperd through the engine.