Thin or thick: an excerpt from a classic ASTM book

[Gokhan]

I've just downloaded the classic 1989 ASTM book by James A. Spearot titled "High-temperature, high-shear oil viscosity."

The following excerpt from page 53 that ends the subsection called "Engine-wear studies" is so stunning that I had to create a thread on it. It debunks everything the thick-oil people claim:

'In a series of engine-dynamometer, bearing-wear studies, Heath et al. [22] tried to "fail"
engine bearings by operating them with extremely "light" viscosity oils during severe
(although short) steady-state lugging and snap acceleration/lugging tests in a 3.8 L engine.
A well-formulated, SAE 5W oil which was expected (based on its viscometric characteristics)
to fail during the test series performed well even though its HTHS viscosity at 150 °C
and l06 s-1 was 1.4 cP (0.0014 Pa·s). Bearing distress during these tests was discovered to
be more a function of engine mechanical parameters (initial bearing clearance and oil-feed
pressure) than oil rheological properties. It is hypothesized, however, that engine-bearing
wear in customer service may be influenced by the passage of oil contaminants through
the point of minimum oil film thickness in the bearing; a variable which is controlled by
oil rheological properties.'

 

[Ethan1]

The last sentence in the quote which you posted means that the test did not accurately simulate a typical engine.

 

[Gokhan]

Originally Posted By: Ethan1
The last sentence in the quote which you posted means that the test did not accurately simulate a typical engine.

That's not true. They used a real, typical engine. However, it was a bench test, not a field test. That's what the last sentence means.

 

[igs]

????

If 5W causes engines to fail manufacturers would not be putting 0W in their engines. The point isn't thin oil causes engines to fail but it provides less protection than thick oil which in indisputable.

 

[OVERKILL]

I think this is a critical component here:

Quote:
tried to "fail" engine bearings by operating them with extremely "light" viscosity oils during severe (although short) steady-state lugging and snap acceleration/lugging tests in a 3.8 L engine.


Generally, the recommendation for heavier oils is for prolonged periods that will elevate oil temperature. If you are doing short bursts, that's not an issue. That's why NASCAR qualifying cars run significantly lighter oils than they do in the main event, that's why GM recommends 15w-50 in place of 5w-30 when extremely high oil temperatures are to be expected. If you don't have the opportunity to push the temperature, you don't need the buffer.

 

[Gokhan]

Originally Posted By: igs
????

If 5W causes engines to fail manufacturers would not be putting 0W in their engines. The point isn't thin oil causes engines to fail but it provides less protection than thick oil which in indisputable.

It's not "5" as in SAE 5W-30. It's "5" as in 0W-5. Such an oil hasn't even been proposed yet. The lightest oil that has been proposed is SAE 0W-8, which has an HTHSV minimum of 1.7 cP. The "SAE 5W" oil used in the paper will be like when SAE 0W-4 is proposed in the distant future, which will have an HTHSV minimum of 1.4 cP.

 

[Shannow]

Real world bearing tests, in real world operation...

 

[Gokhan]

Originally Posted By: OVERKILL
I think this is a critical component here:

'... tried to "fail" engine bearings by operating them with extremely "light" viscosity oils during severe (although short) steady-state lugging and snap acceleration/lugging tests in a 3.8 L engine.'

I think this is the real critical component:

'Bearing distress during these tests was discovered to be more a function of engine mechanical parameters (initial bearing clearance and oil-feed pressure) than oil rheological properties.'

Therefore, it's the bearing and lubrication design that matters most, not the oil viscosity.

 

[Shannow]

Why then in an ASTM task force would Spearot conclude...

Quote:
In 1984, an ASTM task force finished reviewing the available literature and composed a report that summarized the effects of viscosity on bearing oil film thickness, engine wear, engine friction, and fuel economy (ASTM DS-62). This paper reviews the findings of that report and updates them in light of recent studies. The case for incorporating HTHS viscosity specifications into the Engine Oil Viscosity Classification, SAE J300, is presently stronger than ever.


if the measure was irrelevant ?

 

[Shannow]

Originally Posted By: Gokhan

I think this is the real critical component:

'Bearing distress during these tests was discovered to be more a function of engine mechanical parameters (initial bearing clearance and oil-feed pressure) than oil rheological properties.'

Therefore, it's the bearing and lubrication design that matters most, not the oil viscosity.


I think that the critical component is the whole paragraph, not where you left it off.

For those wanting to see the rest of the paragraph...

The quoted paper

Go to page 53...then page 57

 

[Gokhan]

Originally Posted By: Shannow
For those wanting to see the rest of the paragraph...

The quoted paper book

Go to page 53... then page 57

Well, I did quote the entire paragraph in my original post.

 

[Shannow]

Originally Posted By: Gokhan
Originally Posted By: Shannow
For those wanting to see the rest of the paragraph...

The quoted paper book

Go to page 53... then page 57

Well, I did quote the entire paragraph in my original post.

But left out the MOFT versus viscosity as the key driver of wear in your "most important point" ???

 

[dblshock]

let me know once they figure it all out, meanwhile my Honda runs sweet on 0/40 in the heat.

 

[dblshock]

the author has a speak like a Alan 'Greenie' Greenspan...take it any way you like.

 

[Rolla07]

Originally Posted By: dblshock
let me know once they figure it all out, meanwhile my Honda runs sweet on 0/40 in the heat.


Rofl...ur car is new, hopefully it runs sweet on any oil. Mine runs great on any oil. Alot of members have proven thin works great. This debate will never die.

 

[igs]

Originally Posted By: Gokhan
Originally Posted By: igs
????

If 5W causes engines to fail manufacturers would not be putting 0W in their engines. The point isn't thin oil causes engines to fail but it provides less protection than thick oil which in indisputable.

It's not "5" as in SAE 5W-30. It's "5" as in 0W-5. Such an oil hasn't even been proposed yet. The lightest oil that has been proposed is SAE 0W-8, which has an HTHSV minimum of 1.7 cP. The "SAE 5W" oil used in the paper will be like when SAE 0W-4 is proposed in the distant future, which will have an HTHSV minimum of 1.4 cP.


Right, so expect lighter and lighter proposals in the future.

 

[igs]

Originally Posted By: Gokhan
Originally Posted By: OVERKILL
I think this is a critical component here:

'... tried to "fail" engine bearings by operating them with extremely "light" viscosity oils during severe (although short) steady-state lugging and snap acceleration/lugging tests in a 3.8 L engine.'

I think this is the real critical component:

'Bearing distress during these tests was discovered to be more a function of engine mechanical parameters (initial bearing clearance and oil-feed pressure) than oil rheological properties.'

Therefore, it's the bearing and lubrication design that matters most, not the oil viscosity.


Bearing design is not anything the end user has control over. Oil viscosity is.

 

[igs]

Originally Posted By: dblshock
let me know once they figure it all out, meanwhile my Honda runs sweet on 0/40 in the heat.


It would run sweeter with 0/60

 

[PeterPolyol]

Originally Posted By: Gokhan
It is hypothesized, however, that engine-bearing
wear in customer service may be influenced by the passage of oil contaminants through
the point of minimum oil film thickness in the bearing; a variable which is controlled by
oil rheological properties.'

Suppose if contaminants passing through the area of MOFT are of a small enough size, they should not breach MOFT and subsequently not abrade the bearing surface. Conversely, if they are large enough to breach the MOFT, then I take it that is where the author's concern comes from regarding the presence of contamination. I'd hypothesize (about their hypothesis) that a smaller bearing clearance reduces the particle-size requisite and the MOFT threshold before abrasive damage occurs? Sadly, Google blocked the referenced pages out from the preview.

Originally Posted By: Gokhan

I think this is the real critical component:

'Bearing distress during these tests was discovered to be more a function of engine mechanical parameters (initial bearing clearance and oil-feed pressure) than oil rheological properties.'

Therefore, it's the bearing and lubrication design that matters most, not the oil viscosity.


Oil-feed pressure, that's interesting. Curious about what way they meant

 

[beanoil]

Originally Posted By: Gokhan
Originally Posted By: OVERKILL
I think this is a critical component here:

'... tried to "fail" engine bearings by operating them with extremely "light" viscosity oils during severe (although short) steady-state lugging and snap acceleration/lugging tests in a 3.8 L engine.'

I think this is the real critical component:

'Bearing distress during these tests was discovered to be more a function of engine mechanical parameters (initial bearing clearance and oil-feed pressure) than oil rheological properties.'

Therefore, it's the bearing and lubrication design that matters most, not the oil viscosity.


And I think this is the real critical component here:
'It is hypothesized, however, that engine-bearing
wear in customer service may be influenced by the passage of oil contaminants through
the point of minimum oil film thickness in the bearing; a variable which is controlled by
oil rheological properties.'
It's been said many, many times here that the oil film must be thicker than the contaminants. The balance is, and always has been, to have a thick enough oil film at a given temperature and keep contaminants in check through filtration and dispersants to minimize wear.