Viscosity Index Improvers are not bad.

[KrisZ]

Originally Posted By: ExMachina

Originally Posted By: Oil Changer
If it pumps, it's not too thick. An 15W or 20W-XX is not too thick at 20F; it will pump.


Thats the common fallacy. I tried to dispel that a while back. Fact is, oil needs to avoid tripping the max pressure relief valve at the pump, at the oil filter (bypass) too, and then get into tight clearances once its up in various places inside the engine for lubrication to happen cold. Thick oil has trouble running that gauntlet of physics.


Then why is the MRV limit set to a massive 60,000cP for each W rating? Even the cold cranking simulator test limit is set at a pretty hefty 3500cP.
And don't forget that the clearances get bigger as the temperature drops.

 

[ExMachina]

Originally Posted By: KrisZ
Originally Posted By: ExMachina

Originally Posted By: Oil Changer
If it pumps, it's not too thick. An 15W or 20W-XX is not too thick at 20F; it will pump.


Thats the common fallacy. I tried to dispel that a while back. Fact is, oil needs to avoid tripping the max pressure relief valve at the pump, at the oil filter (bypass) too, and then get into tight clearances once its up in various places inside the engine for lubrication to happen cold. Thick oil has trouble running that gauntlet of physics.


Then why is the MRV limit set to a massive 60,000cP for each W rating? Even the cold cranking simulator test limit is set at a pretty hefty 3500cP.
And don't forget that the clearances get bigger as the temperature drops.


Because that is all the current technology can give us. It is what's generally achievable, so the spec is written that way. If we lived in a Star Trek future world, then Scotty would have an oil that would be a mere 1,000cp in the MRV test. See:

 

[OVERKILL]

Originally Posted By: ExMachina
Originally Posted By: KrisZ
Originally Posted By: ExMachina

Originally Posted By: Oil Changer
If it pumps, it's not too thick. An 15W or 20W-XX is not too thick at 20F; it will pump.


Thats the common fallacy. I tried to dispel that a while back. Fact is, oil needs to avoid tripping the max pressure relief valve at the pump, at the oil filter (bypass) too, and then get into tight clearances once its up in various places inside the engine for lubrication to happen cold. Thick oil has trouble running that gauntlet of physics.


Then why is the MRV limit set to a massive 60,000cP for each W rating? Even the cold cranking simulator test limit is set at a pretty hefty 3500cP.
And don't forget that the clearances get bigger as the temperature drops.


Because that is all the current technology can give us. It is what's generally achievable, so the spec is written that way. If we lived in a Star Trek future world, then Scotty would have an oil that would be a mere 1,000cp in the MRV test. See:


No.

Many (most?) oils are no where NEAR the 60,000cP limit. The limit used to be lower, at 40,000cP, but was revised as it was demonstrated that oil pumpability wasn't effected until over the 60,000cP threshold except in the case of a very few extremely old engines, one of them an Aussie design IIRC.

There's an entire paper on the CCS and MRV limits, why they are set to what they are and what conditions they are designed to replicate.

 

[ExMachina]

Originally Posted By: OVERKILL
Originally Posted By: ExMachina
Originally Posted By: KrisZ
Originally Posted By: ExMachina

If it pumps, it's not too thick. An 15W or 20W-XX is not too thick at 20F; it will pump.


Thats the common fallacy. I tried to dispel that a while back. Fact is, oil needs to avoid tripping the max pressure relief valve at the pump, at the oil filter (bypass) too, and then get into tight clearances once its up in various places inside the engine for lubrication to happen cold. Thick oil has trouble running that gauntlet of physics.


Then why is the MRV limit set to a massive 60,000cP for each W rating? Even the cold cranking simulator test limit is set at a pretty hefty 3500cP.
And don't forget that the clearances get bigger as the temperature drops.


Because that is all the current technology can give us. It is what's generally achievable, so the spec is written that way. If we lived in a Star Trek future world, then Scotty would have an oil that would be a mere 1,000cp in the MRV test. See:

No.

Many (most?) oils are no where NEAR the 60,000cP limit. The limit used to be lower, at 40,000cP, but was revised as it was demonstrated that oil pumpability wasn't effected until over the 60,000cP threshold except in the case of a very few extremely old engines, one of them an Aussie design IIRC.

There's an entire paper on the CCS and MRV limits, why they are set to what they are and what conditions they are designed to replicate.


overkill, you are missing the point. The question was why the visc is thick in those cold cranking standards, and I state that physics demand an oil to be thick cold. Thats all. Then I went on to say they set spec to allow for current technology to create a product to meet the spec. IF current tech could easily & cheaply create an oil that has a much a lower MRV or CCS viscosity, then the specs could reflect that.

Still, the bigger overall point of pushing thick honey around is true. If thick, it just doesn't get into the tight clearances.

Remember, specs are often created by panels of the very people whose companies will have to implement the spec with an actual product, so extreme specs are kept out.

 

[Blue_Angel]

Originally Posted By: KrisZ
And don't forget that the clearances get bigger as the temperature drops.

?
Can you please explain this.

 

[OVERKILL]

Originally Posted By: ExMachina


overkill, you are missing the point. The question was why the visc is thick in those cold cranking standards, and I state that physics demand an oil to be thick cold. Thats all. Then I went on to say they set spec to allow for current technology to create a product to meet the spec. IF current tech could easily & cheaply create an oil that has a much a lower MRV or CCS viscosity, then the specs could reflect that.


I'm not missing the point, but it would appear you are misunderstanding the purpose of the CCS and MRV tests.

The MRV test is designed to replicate the ability of an oil to be drawn by the pump, through the pick-up tube, into the oil pump. The old limit for that test, was, based on engines that were current at the time, 40,000cP, as beyond that, certain engine designs were incapable of drawing oil.

As time marched on and designs evolved, that spec was changed as well, to reflect the capabilities of modern sump/pump/pickup assemblies, which could draw oil that was at least 60,000cP into the pump.

This is JUST a limit, no production lubricant for a given W-designation comes even close to it. Even M1 0w-40 has an MRV of ~31,000cP @ -40C, roughly half the limit. The purpose of the limit on the MRV test is to just define the boundary of where an oil can no longer be drawn by the pump, that's it! Companies then publish (and some don't) their results in this test, which are always far, FAR lower than the limit.

Originally Posted By: ExMachina
Still, the bigger overall point of pushing thick honey around is true. If thick, it just doesn't get into the tight clearances.


Which tight clearances in particular? Any part of the engine that is pressure-fed will get oil very shortly after start-up, even if that oil is extremely thick. Non-pressure-fed areas will still have residual oil in them from the last time the engine was operated; it isn't like somebody got in there with a can of brake kleen and hosed down the internals. The oil also thins very quickly after start-up; the amount of heat generated is significant and the shearing effect the bearings have on the lubricant works to heat it very quickly. During that brief period of time that the oil cannot "creep" into these tight clearances you speak of, those areas are still being lubricated by the thick oil that was already in there and will be less inclined to leave that area because it is still thick and cold.

Originally Posted By: ExMachina
Remember, specs are often created by panels of the very people whose companies will have to implement the spec with an actual product, so extreme specs are kept out.


These specs are not of that type. CCS is designed to replicate the viscosity at which it affects the ability for an engine to crank. MRV is, as I already noted, designed to set a hard limit on where the oil is no longer able to be drawn up by the pump. They aren't "performance targets" that have been dumbed down by the oil companies so that the products can meet them, they are simply limits set based on extensive engine testing that then work to set which W-classification an oil falls into.

From what I've seen your typical PCMO will run into the CCS ceiling (which is MUCH lower) before it hits the MRV limit. These two tests define the W-grading system and their limits are what they are based on what engine tests show to be the limit of acceptability, not what is "easier" for the oil companies. A product like M1 0w-20 has an MRV of 9,200cP and is significantly below the CCS limit as well. As I noted, even M1 0w-40 hits well below the limits for the 0w-xx designation and that's the hardest designation to obtain with temperature targets of -35C and -40C respectively. For a 5w-xx, 10w-xx, 15w-xx or 20w-xx, being within the limits for the desired W-rating is even easier, as a PAO-based xW-30 is possible to meet the 10w or even 5w rating without any VII's. A quick glance at some of XOM's PAO data sheets will demonstrate how good the extreme low temperature capability of some of the base oils by themselves can be.

 

[KrisZ]

Originally Posted By: Blue_Angel
Originally Posted By: KrisZ
And don't forget that the clearances get bigger as the temperature drops.

?
Can you please explain this.


All metals contract and expand with temperature. Different metal types and alloys do it at different rates, but they all do it.

For example, holes will get bigger as the temp. drops and get smaller as temps. rise. Shafts on the other hand are opposite, their OD will get smaller as the temps. drop and bigger as the temps rise.
That is why an engine can seize if overheated because while the cylinder walls shrink, the piston will expand and that is why some engines have piston slap when started in very low temperatures.
The same principle, in varying degrees, applies to all components in the engine.

 

[ExMachina]

overkill, good points on the business of CCS and MRV specs. I feel like we are talking about 2 different things though.
I was responding to the statement "if it pumps, its not too thick" thing I strongly disagree with. Then the subject of why the CCS or MRV viscosity limits are in the thousands. My point is that we COULD have CCS limits be around 500 instead of 3,500 if all the oil makers felt comfortable with that Star Trek level of tech.

 

[KrisZ]

Originally Posted By: ExMachina
overkill, good points on the business of CCS and MRV specs. I feel like we are talking about 2 different things though.
I was responding to the statement "if it pumps, its not too thick" thing I strongly disagree with. Then the subject of why the CCS or MRV viscosity limits are in the thousands. My point is that we COULD have CCS limits be around 500 instead of 3,500 if all the oil makers felt comfortable with that Star Trek level of tech.


You may strongly disagree with it, but it doesn't make it any less relevant. Your "Start Trek" oil's benefits are only in your imagination and not backed by any SAE papers.

The tests mentioned above were developed exactly to ensure that the engine is protected. If you bothered to read some of them, you would see that there was an increase in engine failure rate, not because the oils were too thick to get to the tight places, but because they could not be pumped.

 

[hatt]

Quote:
Still, the bigger overall point of pushing thick honey around is true. If thick, it just doesn't get into the tight clearances.
Which commonly used PCMO isn't going to easily make it in those clearances in above freezing temps? Even 0F. You guys like to confuse common temps encountered with extreme Siberia winter conditions.

 

[A_Harman]

Originally Posted By: Blue_Angel
Originally Posted By: KrisZ
And don't forget that the clearances get bigger as the temperature drops.

?
Can you please explain this.


Yes, with aluminum blocks and iron cranks, the bearing clearances will tighten as the temperature goes below room temperature.

 

[A_Harman]

Originally Posted By: KrisZ
Originally Posted By: Blue_Angel
Originally Posted By: KrisZ
And don't forget that the clearances get bigger as the temperature drops.

?
Can you please explain this.


All metals contract and expand with temperature. Different metal types and alloys do it at different rates, but they all do it.

For example, holes will get bigger as the temp. drops and get smaller as temps. rise. Shafts on the other hand are opposite, their OD will get smaller as the temps. drop and bigger as the temps rise.
That is why an engine can seize if overheated because while the cylinder walls shrink, the piston will expand and that is why some engines have piston slap when started in very low temperatures.
The same principle, in varying degrees, applies to all components in the engine.


You've got this all bass-ackwards. Holes get bigger as the temperature rises. Shafts also get bigger as the temperature rises. The problem comes from differential rates of thermal expansion between the two, if the block is made of aluminum, and the crank was made of iron.

The cylinder walls don't shrink when an engine heats up. They expand, but because the piston expands more, it closes the clearance.

 

[Blue_Angel]

A-Harman, you beat me to it.

 

[Garak]

Originally Posted By: ExMachina
I was responding to the statement "if it pumps, its not too thick" thing I strongly disagree with.

I'd disagree with that statement, too. But, what would have to be done to get extremely attractive MRV numbers? Lots of things can be "done," but there are compromises. Will the oil lack shear resistance? Would it have problems with other components of the specifications it's trying to meet, be it ILSAC, ACEA, or proprietary? Is it going to cost $20 a liter?

And we know it's not going to make a lick of measurable difference to engine longevity. I like using a proper grade for cold starts, but since just about every vehicle on the road specifies something with a 5w-XX or a 0w-XX, that problem has been solved a long time ago.

 

[KrisZ]

Originally Posted By: A_Harman
Originally Posted By: KrisZ
Originally Posted By: Blue_Angel
Originally Posted By: KrisZ
And don't forget that the clearances get bigger as the temperature drops.

?
Can you please explain this.


All metals contract and expand with temperature. Different metal types and alloys do it at different rates, but they all do it.

For example, holes will get bigger as the temp. drops and get smaller as temps. rise. Shafts on the other hand are opposite, their OD will get smaller as the temps. drop and bigger as the temps rise.
That is why an engine can seize if overheated because while the cylinder walls shrink, the piston will expand and that is why some engines have piston slap when started in very low temperatures.
The same principle, in varying degrees, applies to all components in the engine.


You've got this all bass-ackwards. Holes get bigger as the temperature rises. Shafts also get bigger as the temperature rises. The problem comes from differential rates of thermal expansion between the two, if the block is made of aluminum, and the crank was made of iron.

The cylinder walls don't shrink when an engine heats up. They expand, but because the piston expands more, it closes the clearance.


Looks like I did, thanks for correcting me.

Still, the concept applies that clearances do not stay the same with temperature, but change and most component materials are chosen with this in mind.
I'm not sure what kind of engine designer would select two materials that would tighten the clearance when cold and cut off the oil supply.

 

[ExMachina]

Originally Posted By: Garak
Originally Posted By: ExMachina
I was responding to the statement "if it pumps, its not too thick" thing I strongly disagree with.

I'd disagree with that statement, too. But, what would have to be done to get extremely attractive MRV numbers? Lots of things can be "done," but there are compromises. Will the oil lack shear resistance? Would it have problems with other components of the specifications it's trying to meet, be it ILSAC, ACEA, or proprietary? Is it going to cost $20 a liter?

And we know it's not going to make a lick of measurable difference to engine longevity. I like using a proper grade for cold starts, but since just about every vehicle on the road specifies something with a 5w-XX or a 0w-XX, that problem has been solved a long time ago.


Garak, all true. There is a cost-benefit issue here too.
Also, Overkill and others probably do have a point that thick, gooey oil is up inside a cold engine sticking to parts to some extent, kind of like acting similar to grease on a 0 degF cold start day. I still believe the engine would wear less if the oil coming up from the cold sump were thinner though, since the cold thick gooey oil in there gets knocked out quickly before the circulating engine oil can get to it. Maybe thats where the balance is, thin enough to take over lubrication soon after start up, and thick enough to glop-on to parts during the first few seconds of a cold start.

Its true UOAs don't show appreciably higher iron ppm in the oil on winter oil. Some I remember might have, but by and large modern engines survive nicely.

 

[OVERKILL]

Originally Posted By: ExMachina
My point is that we COULD have CCS limits be around 500 instead of 3,500 if all the oil makers felt comfortable with that Star Trek level of tech.


Except they wouldn't because they are literally just limits, those set by testing with engines as to the specific point where viscosity affects the ability to crank (CCS) and the ability for oil to be drawn up the pick-up and pumped (MRV). Whether we had oils readily available with a CCS of 50 and an MRV of 500, it wouldn't matter, as the limits themselves don't change, follow?

There's no policy with respect to CCS/MRV that is stopping formulators from making oils that score obscenely well below the limits of the testing protocols. I already cited one example with AFE 0w-20 which is likely batting at your 500 value if we were to test its CCS/MRV at the testing temperatures for a 10W for example. The limiting factors are base oil low temp capability and the effectiveness of PPD's and VII's in controlling those numbers but we need to be sure that we are talking about the same thing as we've just covered two completely separate topics!

1. CCS/MRV as they define LIMITS in terms of cranking and pumpability for a given W-designation
2. The MEASURE of CCS/MRV as a barometer for oil cold flow capability separate from the limits they represent

Regarding point 1, these limits will not change because of what they represent, which itself doesn't change whether we've got moon sauce oil formulas going on or not.

Pursuing #2 is already being done by many members here including myself. Chasing oils with "superior" cold temperature capabilities. A glance at a PDS for a product can often give you an oil's capability in this regard. You can also extrapolate these numbers backwards in 5 degree increments by halving them to get a rough idea of what the CCS and/or MRV are for that product at a higher testing temperature.

Note that since CCS and MRV use two completely different testing methodologies, the numbers for each cannot be compared; you cannot contrast CCS with MRV.

 

[Shannow]

Have posted the results of the study on cold pumping time to get through to rocker arm flow many times, and the fact is that if the oil is remotely suitable, within it's pumpability limits (not the Esso video, where only one of the test oils is appropriate for the conditions), the time for oil to flow to the remote portions is the same.

The lower W ratings just let that occur at lower and lower temperatures.

With an appropriate W rating, the galleries get filled at the same rate.

Bearings will draw from the pressurised galleries only what they need, the fallacy that's repeated all the time on BITOG that the relief must be closed, and all of the oil must flow through the engine are just plain wrong.

If the oil is "clumping", "grease like", it's displaying a yield point, and is clearly being operated below it's operating temperature.

A 20W can't display those properties at any temperature above -20C and be called a 20W...use it temperatures even below freezing, and your engine won't know the difference.

As an aside, Citgo 20W20 is about half the viscosity of M1 0W40 at 0C...which will protect a starting engine better ?

 

[Shannow]

Originally Posted By: A_Harman
You've got this all bass-ackwards. Holes get bigger as the temperature rises. Shafts also get bigger as the temperature rises. The problem comes from differential rates of thermal expansion between the two, if the block is made of aluminum, and the crank was made of iron.


Have read a few articles re light aircraft engines cooling to the point of clamping the crank, and the stiffness being blamed for viscosity of the oil.

 

[Shannow]

Woke up to this this morning...

Nissan OEM specs 15W40, GM 20W50 (15W40 in "cold")...both fine.