Cold Oil Questions...

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I often see these vids depict heavy oil poured out like a molasses while cold, but engines don't pour oil they pump it and pressurize it, so I wonder how and if that changes this characterization?
 
Yes and no. The oil's fluidity will certainly effect how well it flows through the sump and downstream areas, but pouring oil or its kinematic viscosity is a low shear rate viscosity measurement and pumping is more dependent on the dynamic viscosity, a high shear rate viscosity measurement.

The "pour test" would be more applicable to gear oils without circulation than it is to engine oils.

That all being said, it will still give you a general idea of an oil's behavior at low temperature compared to another oil. But going with CCS and The rotary viscometer data from SAE testing is much more dependable.
 
I think of paint, thick and gooey in a bucket put into a pressurized sprayer almost vaporizes at the nozzle, no?
 
That is probably a good analogy, but I don't know enough about paint to tell you why that is.
happy2.gif
 
well these cold pour displays must be inaccurate because there's no way that fluid gets to the piston skirts unless pressure changes the fluid dynamic dramatically, thats what I'd suspect.
 
These kind of cold pour tests are measuring the oil's ability to flow under its own weight, sort of like a homegrown low shear viscosity test. This property is important because if the oil can't flow, the oil pump pick-up will suck a hole in the sump oil that will not refill, causing the pump to suck air and leading to oil starvation. Thousands of engines seized back in the early 80s by this mechanism from an oil using a VI improver that gelled the oil under certain temperature cycles.

These homegrown cold pour tests, however, are not well controlled, and even if they were do not tell the whole story. The oil pump will move even a gelled oil through the engine because it creates shear that breaks any weak jelling structures from residual waxes. Think of Jello - it is a weakly jelled liquid that behaves like a solid, but you can still suck it up through a straw by applying vacuum to the top of the straw. The straw, however, leaves a hole in the Jello because it cannot flow under its own weight to refill the hole, and you wind up sucking air. So long as the oil flows and refills the hole left by the sucking action of the oil pump, the engine will be lubricated.

The Cold Crank Simulator (CCS) is a high shear test run on motor oils to confirm that the pump can move a cold viscous oil sufficiently, and the Mini Rotary Viscometer (MRV) is run to confirm that the cold sump oil will flow back into the hole under its own weight. These two tests are much more telling with respect to an oils performance at low temperatures than simple uncontrolled pouring tests, and they are required by the API specifications, while a pour point is not.

Tom NJ/VA
 
Cold thick oil takes a little longer to get to the pistons and lube the cylinder walls.

But you can do your own pour test:

2 identical cups
1 freezer
1 synthetic oil, any grade you use
1 conventional oil, same grade
pour equal amounts in each cup
freeze for 2 hours
pour
observe huge difference is flow rate! surprising!
 
Originally Posted By: Tom NJ
These kind of cold pour tests are measuring the oil's ability to flow under its own weight, sort of like a homegrown low shear viscosity test. This property is important because if the oil can't flow, the oil pump pick-up will suck a hole in the sump oil that will not refill, causing the pump to suck air and leading to oil starvation. Thousands of engines seized back in the early 80s by this mechanism from an oil using a VI improver that gelled the oil under certain temperature cycles.

These homegrown cold pour tests, however, are not well controlled, and even if they were do not tell the whole story. The oil pump will move even a gelled oil through the engine because it creates shear that breaks any weak jelling structures from residual waxes. Think of Jello - it is a weakly jelled liquid that behaves like a solid, but you can still suck it up through a straw by applying vacuum to the top of the straw. The straw, however, leaves a hole in the Jello because it cannot flow under its own weight to refill the hole, and you wind up sucking air. So long as the oil flows and refills the hole left by the sucking action of the oil pump, the engine will be lubricated.

The Cold Crank Simulator (CCS) is a high shear test run on motor oils to confirm that the pump can move a cold viscous oil sufficiently, and the Mini Rotary Viscometer (MRV) is run to confirm that the cold sump oil will flow back into the hole under its own weight. These two tests are much more telling with respect to an oils performance at low temperatures than simple uncontrolled pouring tests, and they are required by the API specifications, while a pour point is not.

Tom NJ/VA

Well said. The cold pour is a part of the picture, but not all of it. The straw in jello is a great analogy.
Also you have to remember that the oil still has to drain back down to the pan once pumped, so the oil pump may be able to suck the pan dry if the oil does not drain back down on it's own fast enough, which is exactly what the cold pour tests show.
 
Originally Posted By: dblshock
I think of paint, thick and gooey in a bucket put into a pressurized sprayer almost vaporizes at the nozzle, no?


I see your point, but the paint has to be thinned to atomize [flow] going through a sprayer. Thick paint would squirt out, then pause while the pressure builds up enough to push it out again until it is thinned enough to flow properly.
 
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Originally Posted By: Ohle_Manezzini
He poured a 10w60 at 6F? Who use a track car at 6F without a preheat? Non sense.


It's not a track car. It's a street car, that happens to do pretty well at the track. I know 15+ people here in the PNW that daily an E46 or E92 M3. All use 10W-60.
 
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I'm sure BMW must account for that 10/60 oil spec in cold weather, but just viewing these frigid pour tests I'm thinking no way, it has to transform under pressure.
 
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This vid guy also mentions the M3 bearing tolerances are the tightest on earth, so much for the thin oil arguement.
 
ok I have been thinking about this video since I saw it recently as I subscribe to that guys videos. He mentioned tracking a car with 0w20 and then doing an oil analysis.He said the analysis came out great but since he tracked it, it wouldnt be a good oil. DIdnt the test just tell us that that is incorrect? It would seem to me that even the oil temp got hot and surely the oil thinned out to lower than the 20 grade, it still protected the engine sufficiently. Am I missing something here?
 
Originally Posted By: E150GT
ok I have been thinking about this video since I saw it recently as I subscribe to that guys videos. He mentioned tracking a car with 0w20 and then doing an oil analysis.He said the analysis came out great but since he tracked it, it wouldnt be a good oil. DIdnt the test just tell us that that is incorrect? It would seem to me that even the oil temp got hot and surely the oil thinned out to lower than the 20 grade, it still protected the engine sufficiently. Am I missing something here?


Right, I caught that too, 'catastrophic' he mentions yet no UOA wear metals? but I was more focused on understanding how that 10/60 could pump under pressure at 6F when the natural flow seems so very thick. In my U.P. garage I admit most oils I use look similar at 0F or below, the fluid must be changing under pressure. wonder how my father or granfather ever ran a car through winter here 50-80 years ago..pressurizing must be the key.
 
Originally Posted By: dblshock
I'm sure BMW must account for that 10/60 oil spec in cold weather, but just viewing these frigid pour tests I'm thinking no way, it has to transform under pressure.


Originally Posted By: dblshock
Right, I caught that too, 'catastrophic' he mentions yet no UOA wear metals? but I was more focused on understanding how that 10/60 could pump under pressure at 6F when the natural flow seems so very thick. In my U.P. garage I admit most oils I use look similar at 0F or below, the fluid must be changing under pressure. wonder how my father or granfather ever ran a car through winter here 50-80 years ago..pressurizing must be the key.


In general viscosity does not change with pressure. It is possible that can increase with pressure, but not at the pressures in an ICE.

Viscosity changes with shear if the fluid is thixotropic. But the main influence is temperature. You can say they "look similar" but they aren't.

Why do you think a 10W oil can't pump at 6F?
 
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