All You Guys That Think OEM Recommended 16 or 20 Weight...

[CumminsMech]

It was a response to Cumminsmech, which I forgot to quote. Those are HDEO oils, Mobil 1 is not. Neither are they A3/B4 or C3 oils, btw...

Yup you are correct those are HDEO oils. I just wanted to illustrate that Cummins and the heavy duty industry is also moving towards thinner oils in many applications. They're also trying to squeak out any additional MPG's where they can, thinner oil being just 1 of the changes. 0.5 mpg over the course of a year can be thousands of dollars saved and most fleets don't haul the full 80k lbs. Our performance engines still spec 15w-40, but they usually haul well over 100k pounds and MPG's are expected to be worse.

So it's pretty much the same solution to the many debates on here. Your viscosity highly depends on how you intend to use that vehicle. You'll be fine with the thinner OEM spec with light duty/commuter use. With high idle time/stop n go/heavy foot/towing, you may want to kick it up a notch to the next grade up. 15w-40 HDEO in a new Camry for example is a bit extreme to me, but to each his own. Just my $.02.

 

[ka9mnx]

Doesn't really matter, the fact that some of them do was consistent with my original statement.

Ok, now I see your point.

 

[ZeeOSix]

Correct me if mistaken. But it goes something like this. Thin as possible thick as necessary?

My DD sees 1500rpm for 90% of its life. Therefore it's best to go with the thinnest allowable viscosity as per manufacturer recommendations.

The way hydrodynamic lubrication works in journal bearings shows that the slower the bearing turns the smaller the MOFT will be, and the thicker the oil is the larger the MOFT will be. So if an engine is running at lower RPM it would benefit from a thicker oil viscosity to give more MOFT. One thing you don't want to do is lug an engine at high load at very low RPM while running a thin oil.

 

[nthach]

They’re actually recommending 10w-30 year round in all new 12L coach buses and efficiency series 15L semi engines now. Haven’t seen any oil related issues yet. That being said, most truck fleets still run 15w-40 year round and buses don’t get shut off for long. 5w-40 I think is the sweet spot year round. I’ve used that in all my Cummins, Powerstroke, or 80’s Mercedes diesel engines I’ve had. Ran it in New Mexico/Arizona summers and some Canadian winter trips.

I was behind a New Flyer Xcelsior hybrid bus a few days ago. I was able to make out USE 15W-40 API CK-4 ENGINE OIL through the louvers of the engine bay door. I think it was an ISL, it wasn’t an Allison-equipped bus but a similar BAE Systems series-drive to what NYC and SF use. The mechanics for that agency said they’re still running Delo 400 until Cummins says otherwise.

I’ve seen the local Walmart stock Motorcraft 10W-30 CK-4 oil and Delo FA-4.

 

[blingo]

Makes it sound as if Stribeck had designed a curve for rod or rotor bearing MOFT over the 9krpm or as if per some other artist's impression the revs had been declared no longer the problem. But there's no Stribeck ruling MOFT, of course. The popular curve's purple lullaby's merely illustrating one influence and not MOFT growing happily ever after passing 1500rpm.
The Schüttelhuber may be better off than the rotary, but either way any extended table should be fun to look at.

 

[ZeeOSix]

The popular curve's purple lullaby's merely illustrating one influence and not MOFT growing happily ever after passing 1500rpm.

MOFT is happier at 7500 than at 2500 RPM in this engine. MOFT is going to be less at 1500 RPM. I'm sure that MOFT vs RPM relationship holds true for all other engine journal bearings.

 

[ZeeOSix]

Also ... what this graph is saying in general about how oil viscosity and RPM influences the oil film inside a journal bearing (in an indirect way) is for a given bearing size, as the RPM goes down, the viscosity should go up to protect the bearing (ie, influences the MOFT).

 

[Accent Abuser]

Yup you are correct those are HDEO oils. I just wanted to illustrate that Cummins and the heavy duty industry is also moving towards thinner oils in many applications. They're also trying to squeak out any additional MPG's where they can, thinner oil being just 1 of the changes. 0.5 mpg over the course of a year can be thousands of dollars saved and most fleets don't haul the full 80k lbs. Our performance engines still spec 15w-40, but they usually haul well over 100k pounds and MPG's are expected to be worse.

So it's pretty much the same solution to the many debates on here. Your viscosity highly depends on how you intend to use that vehicle. You'll be fine with the thinner OEM spec with light duty/commuter use. With high idle time/stop n go/heavy foot/towing, you may want to kick it up a notch to the next grade up. 15w-40 HDEO in a new Camry for example is a bit extreme to me, but to each his own. Just my $.02.

No but a thin 5w40/0w40 or 5w30 with 3.5 HTHS would probably be a good trade off for fuel economy and protection in most vehicles.

 

[blingo]

As I got to know this forum, it cannot be a problem to find a pic that shows these numbers upside down and inside out

...so, where's table 7 from, please, or what did they do? Guess I've seen it once, but can't remember.

 

[blingo]

Here could be some rod-MOFT the other way round – what now, my love? We know there's loads developing, viscosities heating down and shearing round and round – no sense in looking at just a pic and being done, right?

Engine Oils and Automotive Lubrication

Discusses all the major aspects of automotive and engine lubrication - presenting state-of-the-art advances in the field from both research and industrial perspectives. This book should be of interest to mechanical, lubrication and automotive engineers, automotive and machinery designers as well...

books.google.de

Another (SAE 930694):

 

[ZeeOSix]

Here could be some rod-MOFT the other way round – what now, my love? We know there's loads developing, viscosities heating down and shearing round and round – no sense in looking at just a pic and being done, right?


View attachment 68224

Engine Oils and Automotive Lubrication

Discusses all the major aspects of automotive and engine lubrication - presenting state-of-the-art advances in the field from both research and industrial perspectives. This book should be of interest to mechanical, lubrication and automotive engineers, automotive and machinery designers as well...

books.google.de

View attachment 68225


Another (SAE 930694):
View attachment 68231

Not so sure about that test data ^^^ ... here's why.

Per Sommerfeld, no matter what the l/d ratio of the bearing is, if the bearing speed (N) goes up, with all other factors in the Sommerfeld Characteristic formula staying constant, the increased bearing speed also makes the Sommerfeld Number "S" go up. The MOFT variable goes up with increased "S", because "ho" (MOFT) will increase (and the eccentricity ratio will also go down) since the bearing clearance "c" is fixed. So Sommerfeld has been wrong for how many years? - lol. All the pieces are shown below so you can see it for yourself.

 

[ZeeOSix]

More ... from King Engine Bearing Specialists. MOFT goes up with viscosity and also goes up with increased RPM.

 

[ka9mnx]

Also note that as oil is compressed it's viscosity goes up.

 

[Obi Wan Noobi]

Also note that as oil is compressed it's viscosity goes up.

Isn't oil a liquid?

 

[kschachn]

Isn't oil a liquid?

Last time I looked. What are you getting at Yogi? Er. I mean Obi?

 

[blingo]

That exactly as so often is the point, ZeeO, an engine doesn't necessarily keep and hold all other things...

Christian came from car engines at 9000rpm on the road before you made it look as if anyone had to be interested in whatever steady loading and stuff to get nothing but whatever behaviour over rpm. So I wanted to know for a start: What were they doing? Same with this King now: Where's the graphing coming from, what was done?

The others were looking at engine bearings in action. Same thing over and over: Not one viscosity, one pressure, one clean liness throughout an engine, engine's life, engine's drive....
One underlying principle, curve, one artist, Stribeck or Sommerfeld, one belief, one book... don't necessarily make the convincing mansplaining killing the reasoning.

What to make, for example, of those SAE numbers? 880681 and 892154

Read there: Sommerfeld, check! I'm good. Or read through 4. and 5.?




Start searching the direction of ultra shear et al. Not new news that HTHS and other beliefs' thicknesses need not even remain so "thick" when against their reluctance making it into an engine bearing which is actually revved. Even under this SAE number there's a start, if only interested.
Reasoning and serious explanations are out there. No modern car is built or studied or modeled or driven based on nothing but a garage lab and its naked Stribeck. Or a pump layout or a rotating disc under the sun etc. pp.

Aspects have placements.

 

[Jetronic]

Makes it sound as if Stribeck had designed a curve for rod or rotor bearing MOFT over the 9krpm or as if per some other artist's impression the revs had been declared no longer the problem. But there's no Stribeck ruling MOFT, of course. The popular curve's purple lullaby's merely illustrating one influence and not MOFT growing happily ever after passing 1500rpm.
The Schüttelhuber may be better off than the rotary, but either way any extended table should be fun to look at.

No, the stribeck curve doesn't show MOFT, it shows friction. Friction which can be within the oil itself, or from metal to metal contact, both to varying degrees.

 

[blingo]

That's clear, but not actually reading it, it's just a curve and becomes a problem. That's what happens here all the time. A pump characteristic can be a pump characteristic in a curve. Then people who are looking at engine use need to even restore the meanings of curves. A rotating disc may just be a rotating disc under the sun and an idea. A religion, fixation, excuse...

Stribeck is not a full mindset to master the silly Autobahn or a cold start or ever arrive at an acute cleanliness with TEOST and Noack in the trunk.

Ni dieu et maître, ni QAnon or HTHS.


Fun fact: An old rotor bearing load curve to a degree looks like a Stribeck design

 

[ZeeOSix]

One underlying principle, curve, one artist, Stribeck or Sommerfeld, one belief, one book... don't necessarily make the convincing mansplaining killing the reasoning.

What to make, for example, of those SAE numbers? 880681 and 892154

View attachment 68276 View attachment 68277

Read there: Sommerfeld, check! I'm good. Or read through 4. and 5.?

You have the Table 4 and Figures 5 and 6 that are referenced in the above snip-it text? Nothing in the snip-it text above says anything about the MOFT decreasing with RPM, even in 4. and 5. conclusions.

What kind of crap oil formulations and VIIs were being used back when those studies were done? I could see that if the oil they used sheared badly at high RPM and high temperature due to formulation, that the MOFT could decrease with increased RPM because the viscosity decrease factor was stronger than the RPM factor in the Sommerfeld bearing number formula numerator. Newer studies seem to show that MOFT increases with increased viscosity and increased RPM, just like Sommerfeld shows.

 

[ZeeOSix]

If a multi-grade oil under HTHS conditions allows a journal bearing to lose significan MOFT with increased RPM, then it's crap oil IMO.

The Bearing Oil Film Thickness of Single and Multi-Grade Oils—Part 1: Experimental Results in a 3.8L Engine

Bearing oil film thickness (BOFT) measurements were obtained in the front main bearing of a 3.8-liter engine. Engine speed, engine load, and oil temperature were varied to determine the effect of these parameters on BOFT. For single-grade engine oils, the minimum oil film thickness (MOFT) correlated

www.sae.org

"For multigrade oils (SAE 5W-30, 10W-30, 10W-40, and 15W-40) MOFT values could not be related to the Sommerfeld number with a high degree of correlation."

But did the MOFT actually decrease the whole time the RPM increased? Where is that data in the study? If that was the case, I'd think the measured HTHS viscosity would also show to be abnormally low for an oil with a specific KV100 grade rating. It's the HTSH viscosity inside the bearing at any instant in time that will determine the MOFT, given that all other factors are held constant.