Does oil freeze?????

[daman]

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I juess i don't now how to say this any clearer,

I'm talking normal winter temps here guy's

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According to this page , the all-time Bad Axe low was -23F on 1/30/1951, which works out to -30C.

Pour point of Mobil SAE 30 is -15C.

Similar to someone just posted great links on cSt measurements, anybody want to post anything on pour points?

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thanks for posting that i was always told -30f..

 

[falconman]

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Ever wonder what NASA uses to lube moving parts on their interplanetary satellites? It's hundreds of degrees below zero out there (like -400F). I'd suspect dry lubricants and fully self-lubricating components and designs.

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They use Pennzane...Same thing that was in Pennzoil Syn.

 

[Tom NJ]

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Similar to someone just posted great links on cSt measurements, anybody want to post anything on pour points?

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There is a difference between pour point and freeze point.

In the pour point test (ASTM D-97), a couple of ounces of oil is placed in a glass cylindrical jar measuring about 1" in diameter and 4" tall. The jar is sealed with a rubber stopper and a thermometer is inserted through the stopper and into the oil with the bulb just below the oil surface. This jar assembly is then cooled at a prescribed rate and the oil is checked every 5°F as it approaches the expected pour point by turning the jar horizontally. If the oil surface moves at all (pours) within 5 seconds, the jar is returned to the cooling bath and to cool another 5°F, and this checking is repeated until it no longer pours. The last temperature at which the oil surface moved is the pour point. (There are some automatic methods being used that differ from this manual method but work on the same principal).

If the oil has no waxes, such as PAOs and esters, the oil remains clear (unless wet) and the pouring stops when the oil is just too thick to pour under it's own weight. If the oil has waxes, freezing may occur, either before or after the pour point is reached.

Freezing occurs when the waxes grow crystal structures that knit together. This crystalline structure usually turns the oil into a white opaque solid (waxy solid as opposed to glass solid) and flowing stops. Sometimes you can see some oil flowing freely behind or within the waxy crystals indicating that the oil would have had a lower pour point had the freezing into crystals not terminated the test. Hence the freeze point is the point at which crystalline structure growth prevents flow (like water turning into ice) as opposed to the oil simply being too thick to flow (pour point).

Petroleum oils have waxes that, depending on how well they are refined, can cause the base oil to freeze at temperatures as high as 0°F or more, well within “normal” temperatures. In reality, however, it doesn’t happen since the finished oils will contain Pour Point Depressants (PPDs) to inhibit the crystal growth and suppress it down to perhaps -40°F, well below “normal” temperatures. Therefore it is unlikely that you will ever encounter a quality motor oil that will freeze on you.

Tom

 

[JAG]

Good info as always Tom. I once put some candle wax in oil and heated it up until the wax melted. I let it cool and saw the wax solidify again. It then looked as you said you saw at really cold temperatures; there was free flowing oil within the wax crytals. Not that candle wax is the same as the impurities in oil but it's similar in effect.

 

[427Z06]

Thanks for the comprehensive info, Tom.

On a related subject, anyone know the length of the typical molecule of Viscosity Index Improver?

 

[Tom NJ]

Hi 427,

VIIs, like all polymers, have a wide distribution of molecular weights. The molecular weights of VIIs generally range from a few thousand to a few million. The weighted average molecular weight is usually in the hundred thousands, and varies with chemistry and shear stability.

If by length you mean number of carbons, that would range from a few hundred to a few hundred thousand with the weighted average in the tens of thousands.

Tom

 

[427Z06]

Well...if you had a polymer with 300,000 carbon-carbon bonds, assuming 1.5 angstroms per bond, wouldn't that make the polymer chain length microns in size?
(Yes, I know this is an oversimplification). Or are the polymers usually coiled up making them a lot smaller than these numbers suggest?

 

[Tom NJ]

VII molecules are very coiled, especially when cold which is why they increase the viscosity index. The coiled molecules present less resistance to flow when cold, and as they partially uncoil with heat they present more resistance to flow, i.e. higher viscosity.

Tom

 

[427Z06]

So we're talking about molecules with the very largest dimension of any maybe 0.5 micron, and that would be a small percentage of the distribution?

 

[MN Driver]

This is an interesting discussion. A great deal of information to consider. I always thought that oils didn't freeze, just as how they don't evaporate and how they don't tend to homogenize with water. I thought that they would just get thick until they were too thick to be usable. I remember watching modern marvels where they were showing north Canadian truckers going up the ice mountains and they showed a bottle of oil tipped over and you could see how it was fluid for awhile and then it solidified preventing the rest of the oil from leaving the bottle but those are at temps that are probably frequently below normal winter united states temperatures. I'd hope they are using a more fitting oil in those temperatures than the dino 15w-40 that most people use here.

It's odd though because now I am considering what things must look like inside the engine on an extremely cold engine with very thick oil. I'm imagining the positive displacement pump used in engines picking up oil and pumping the sump dry as it all stays in the rest of the engine and essentially running out of oil at the pickup screen. I know it doesn't work that way but it's odd to think of fluid dynamics that way. Since the crank and connecting rods don't generally come in contact with the oil in the sump, where does most of the resistance to starting come from in the winter. Is it the effort of pumping the oil that makes the engine difficult/incapable of starting or is it that the oil is so thick in all of the bearings to where it holds them in place?

 

[TallPaul]

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Since the crank and connecting rods don't generally come in contact with the oil in the sump, where does most of the resistance to starting come from in the winter. Is it the effort of pumping the oil that makes the engine difficult/incapable of starting or is it that the oil is so thick in all of the bearings to where it holds them in place?

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MN Driver, this is an excellent question and really is worthy of its own thread. Why don't you make a new thread for it? Also add the reduced cranking ability of the battery in the cold as another factor.

 

[427Z06]

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So we're talking about molecules with the very largest dimension of any maybe 0.5 micron, and that would be a small percentage of the distribution?

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Found my answer.

http://www.polymerchemistryhypertext.com/IdealChain.htm

Sorry for the

diversion.

 

[MGBV8ROADSTER]

The "star" radial polymers appear to improve shear stabilty. Are these in common use?

 

[Tom NJ]

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So we're talking about molecules with the very largest dimension of any maybe 0.5 micron, and that would be a small percentage of the distribution?

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Carbons bond at 120 degree angles so they cannot form a straight line. And with four bonds per carbon they can take off in all directions forming many shapes. I don't know the diameter of the largest molecules in such a polymer mix, but yes they would constitute a very tiny percentage.

Tom

 

[Tom NJ]

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Since the crank and connecting rods don't generally come in contact with the oil in the sump, where does most of the resistance to starting come from in the winter. Is it the effort of pumping the oil that makes the engine difficult/incapable of starting or is it that the oil is so thick in all of the bearings to where it holds them in place?

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Hi MN,

All of the above. Imagine an engine filled with honey - the whole thing becomes a sticky mess and every attempt to move it would consume more energy. The pump would strain to pick it up, it would take more pressure to pump it through small channels, and bearings would become sluggish trying to overcome the resistance. Fortunately some engine parts get real hot real fast, so oil will flow back to the sump before the sump is pumped dry.

Tom

 

[427Z06]

Thanks Tom. I did a little reading on the basics of Polymers. Here's an example of what you describe.

http://www.polymerchemistryhypertext.com/EndToEndDistance.htm

Looks like very few even get to hundredths of microns in length.

 

[lobo11]

I ran a DSC scan over the weekend on some conventional GF3 10w-30. It is a little ragged but I see what looks like a glass transition (Tg) at about -82C. I would like to do a cone and cup on a DMS and see if I can get the Tg from that instead, as it should be much easier to get a definitive point. If I get that sample on I will post.

 

[Vilan]

If your car ever reaches -82C, I think you'd have other problems than worrying about the oil. Like figuring out why someone dumped your car into a pool of liquid nitrogen.

 

[Turbodriven]

How does Motul get to say that their 300v has 0 shear, is it just advertising, or is it that they don't use polymers and therefore there is nothing to shear?