Relationship between an oil's HTHS spec and MOFT

[Slow Car Sport Mode]

Not made intending to represent statements as 100% factual truth; asking for information, to explore and discuss information.

Question: Is an oil's HTHS specification the MAIN one relevant to the MOFT it can provide? And.. then, how is measured MOFT?

HTHS = High Temperature High Shear... This is the specification I personally look at the most since it's probably the most accurate of how the oil is doing in your engine when it's up to speed running on the highway, or really anywhere once fully warmed up. The HTHS spec will determine the second half of the API specification for the grade of oil.. the first number is the W or winter number.

MOFT = Minimum Oil Film Thickness.

Questions:

1. Can MOFT be measured like HTHS? This again partially the basis for this question.. Not the same thing, are they?

2. Is KV100 a better metric for MOFT?

3. Is there any particular characteristic more suited to determine MOFT than HTHS? Does base oil moreso than the fully formulated package (which includes base oil) have some kind of more relevance to this? This again is what I'm hoping to open up to discussion.

Thank you!

 

[Titan]

My guess: Full formulation is what matters.

 

[High Performance Lubricants]

My guess: Full formulation is what matters.

Statement of the year.

 

[4WD]

TCM testing can be found in SAE papers … we can’t post them … you can find them …

 

[tyman]

@kschachn

 

[CR94]

...
Question: Is an oil's HTHS specification the MAIN one relevant to the MOFT it can provide? And.. then, how is measured MOFT? ....

Before others post more elaborate replies, I'll venture that the HTHS specification best corresponds to the risk of MOFT going to zero.

 

[Deleted member 89374]

Can MOFT be measured like HTHS? This again partially the basis for this question.. Not the same thing, are they?

If you don't know the answer to this question then you've been wasting your time here.

Is KV100 a better metric for MOFT?

No, it's not.

Is there any particular characteristic more suited to determine MOFT than HTHS? Does base oil moreso than the fully formulated package (which includes base oil) have some kind of more relevance to this?

 

[ZeeOSix]

1. Can MOFT be measured like HTHS? This again partially the basis for this question.. Not the same thing, are they?

MOFT is the actual physical film thickness (measured in microns - 50u is approx 0.002 inch) of oil between two moving parts. The film that keeps those two parts from rubbing and wearing on each other. HTHS is a viscosity measurement (in centipoise, cP) of oil at a temperature of 150C and a shear rate of 1 million/sec. HTHS viscosity does correlate to the resulting MOFT as one factor - all other factors held constant.

There are other factors involved too when it comes to what the actual MOFT is ... like the relative speed between the moving parts, the force between the two parts, and the actual oil temperature going on in the film layer between the two parts. It could actually be more than 150C, or more shear rate than the 1M/sec rate used to measure HTHS viscosity.

 

[BigTimeTA]

3. Is there any particular characteristic more suited to determine MOFT than HTHS?

Monogrades have a thicker MOFT for a reason. The percentage of VIIs in the oil will certainly increase HTHS relevant to the original base oil viscosity under high shear conditions, yet, in certain full shear engine regions such as piston rings, camshafts, etc, VIIs will no longer contribute to the HTHS viscosity and the original base oil viscosity will show up. HTFS (for full shear conditions) is the more reliable characteristic to judge MOFT because it excludes the viscosity contribution of VIIs that cover the true and original base oil viscosity.

 

[High Performance Lubricants]

While this is true the question remains is will HTFS that is low cause excessive wear? I would maintain it is closer to a 1% problem than a 90% problem. Logic would say if this were the chronic issue some would like to think it is, one we would see a pile of worn out engines (we don’t) or the industry would be chasing the issue (it is not).

Areas in the engine that actually have an issue with increased pressures at the lubrication point directly benefit from the heat/pressure activated ZDDP.

It is the fully formulated oil that matters. Additives really matter. Additives are the Kryptonite to the “I must have the best HTFS number” approach.

 

[ZeeOSix]

While this is true the question remains is will HTFS that is low cause excessive wear? I would maintain it is closer to a 1% problem than a 90% problem. Logic would say if this were the chronic issue some would like to think it is, one we would see a pile of worn out engines (we don’t) or the industry would be chasing the issue (it is not).

You would have to measure the wear difference between two exact engines running the same exact oil, but run one engine at very high RPM to put components into the HTFS realm vs at around or below the HTHS realm. Run them the same number of revolutions, and control the sump temperature to 200F. Run the test on an un-fired engine to keep combustion byproducts out of the oil.

Would camshafts, rings and other components well into HTFS wear more after 100,000,000 revolutions vs not into HTFS? That could be 833 hours at 2000 RPM, and 238 hours at 7000 RPM. Change the oil after 20M revs. Do the same test again but change oil at 50M revs.

I would think there would be a noticable wear difference since film thickness and local oil temperature between moving parts would certainly be different in those two scenarios. Oil formulation can't always replace viscosity in all situations. It would certainly be an interesting test.

 

[4WD]

You would have to measure the wear difference between two exact engines running the same exact oil, but run one engine at very high RPM to put components into the HTFS realm vs at around or below the HTHS realm. Run them the same number of revolutions, and control the sump temperature to 200F.

Would camshafts, rings and other components well into HTFS wear more after 100,000,000 revolutions vs not into HTFS? That could be 833 hours at 2000 RPM, and 238 hours at 7000 RPM. Change the oil after 20M revs. Do the same test again but change oil at 50M revs.

I would think there would be a noticable wear difference since film thickness and local oil temperature between moving parts would certainly be different in those two senarios. Oil formulation can't always replace viscosiy in all situations. It would certainly be an interesting test.

When will you have that test completed ?

 

[ZeeOSix]

When will you have that test completed ?

After you give me $5M. Or you might be able to get it done at the SWRI for just $2M.

 

[Slow Car Sport Mode]

Quick clarifying question here, please.. what is HTFS

HTHS term, I recognize. It is High Tension High Shear.

HTFS I cannot say I recognize.

Please and Thank you.

 

[4WD]

After you give me $5M.

I gave it to a Nigerian Prince instead

 

[Brian123]

While this is true the question remains is will HTFS that is low cause excessive wear? I would maintain it is closer to a 1% problem than a 90% problem. Logic would say if this were the chronic issue some would like to think it is, one we would see a pile of worn out engines (we don’t) or the industry would be chasing the issue (it is not).

Areas in the engine that actually have an issue with increased pressures at the lubrication point directly benefit from the heat/pressure activated ZDDP.

It is the fully formulated oil that matters. Additives really matter. Additives are the Kryptonite to the “I must have the best HTFS number” approach.

Is it true that a cheaper oil would need to be changed sooner than a more expensive or better oil? I am talking about normal driving. I think we can agree that todays oils are made to a price point and whether that is ok for the life of the engine is up to debate.

I am using Mobil 1 ESP 0W-30 and I did notice on the last OCI that the oil came out pretty dark, my car takes 6 quarts of oil, but I did not change the oil filter, so I added 5.5 quarts of oil. What I did notice is that 200 miles into this OCI is that the oil on the dipstick has a slight dark color. This may not mean anything, some may be wondering why I did not change the oil filter, well it is a Fram XG old style oil filter. Maybe these better or more expensive oils clean an engine up better. In the last year I did do alot of short trip driving which I am now trying not to do.

 

[ZeeOSix]

Quick clarifying question here, please.. what is HTFS

HTHS term, I recognize. It is High Tension High Shear.

HTFS I cannot say I recognize.

Please and Thank you.

HTFS is "High Temp Full Shear" ... meaning when the oil shear rate is so high that it fully shears down to essentially it's base viscosity. Note in the example below that at a shear rate of around 10,000,000/sec (10 times higher than the were the HTHS of 1M/sec is measured), the oil viscosity gets to a flat plateau valve depending on it's temperature. That's the HTFS of that oil at that temperature.

 

[ZeeOSix]

Example of HTFS ...

 

[Deleted member 89374]

I did notice on the last OCI that the oil came out pretty dark. I did notice is that 200 miles into this OCI is that the oil on the dipstick has a slight dark color.

That's like Turkish Coffee Fortune Telling...

 

[gregk24]

Example of HTFS ...

Neat video! Now throw some 0w20 in there and watch it run to 300k!