(5w30) 5 when cold 30 when hot?
- Thread starter bkbenjy
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It's all relative. To temperature, in this case. The pre-W number means it flows as well as an SAE X oil would at low temperature (in your example an SAE 5) and flows like a 30 would at 100*C. It doesn't thicken up as it gets hotter. In multi-viscosity oils, it means that the oil doesn't thicken up as much as a straight-weight oil would as the oil cools off.
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The W number describes the oil's cold properties. It's not a rational view of viscosity. It's about pumpability. In a rational view, thicker oil is always thicker oil. It's not really an intuitive concept. Remaining a liquid and pumpable and how thick it is are somewhat divorced.
All multi-weight grade names are in comparison to straight weight grades. A 5w30 is much thinner at operating temperature than it is at 0° (the same as a 30 straight weight), it just is thinner at 0° than a straight weight 30 would be.
In other words, all oils thicken when they get cold, but multi-weights thicken less.
In other words, all oils thicken when they get cold, but multi-weights thicken less.
Originally Posted By: bkbenjy
Does that mean when its cold it starts off as 5 and heats up to 30? That doesn't make sense to me. Wouldn't the cold make oil more solid and heat make it more liquid?
The W number tells you how easy the oil is to pump when it's really cold. The big number tells you how quickly the oil flows when it's hot. They're two entirely different measurements -- pumpability vs. kinematic viscosity -- at two different temperatures. It's like comparing torque at 1,000 RPM with horsepower at 6,000 RPM. Different numbers, different meanings.
At -35º C, a 0w30 and a 0w-40 will be about equally easy to pump. At 100º C, they will both be a lot thinner than they were when cold, but the 0w-20 will thin out more than the 0w-40.
Now, let's take a 0w-40 and a 15w40. At -35º C, the 0w-40 will be pumpable but the 15w40 will be practically solid. At 100º C, they will both be about the same viscosity.
Does that mean when its cold it starts off as 5 and heats up to 30? That doesn't make sense to me. Wouldn't the cold make oil more solid and heat make it more liquid?
The W number tells you how easy the oil is to pump when it's really cold. The big number tells you how quickly the oil flows when it's hot. They're two entirely different measurements -- pumpability vs. kinematic viscosity -- at two different temperatures. It's like comparing torque at 1,000 RPM with horsepower at 6,000 RPM. Different numbers, different meanings.
At -35º C, a 0w30 and a 0w-40 will be about equally easy to pump. At 100º C, they will both be a lot thinner than they were when cold, but the 0w-20 will thin out more than the 0w-40.
Now, let's take a 0w-40 and a 15w40. At -35º C, the 0w-40 will be pumpable but the 15w40 will be practically solid. At 100º C, they will both be about the same viscosity.
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Originally Posted By: Samilcar
Originally Posted By: Gary Allan
It's not really an intuitive concept.
It really isn't, especially when you try to explain it to somebody else.
It's difficult especially if you're not disciplined in the physics behind it. If you are, you can't communicate well with those who are not. I'm not, hence getting those who are to "normal speak" is a challenge. Understanding or rather envisioning the physical event and explaining it intelligently are almost impossible. So, here's the ignorant version
We tend to understand Newtonian concepts of fluids. We stir a beaker or bowl with water in it, it forms a bunch of circles where the mass shears..forms its layers ..faster in the spindle area ..slower as it moves outward. If it's too thick the stuff might just climb the spindle and leave a static mass outside of that immediate zone. If it's cooled more or of a slightly different property, it might just fracture and not remain a liquid at all and have a wad of gel spinning around on it. That's the non-Newtonian realm that we're dealing with when we're looking at cold properties.
..but make no mistake about it. a 5w-40 is always thicker/heavier than a 5w-20. It's not like you get some free ride up to operating temps.
For lack of full grasp of the physics involved, I would merely tell anyone to understand that like terms (5w-20 vs. 5w-40 for example) merely means that it "will pump" at the respective temps noted (-35F or whatever). It won't mean anything beyond that. No "same time to pressure" or anything like that. No "just as easy" in terms of rational flow (my term).
Originally Posted By: Gary Allan
It's not really an intuitive concept.
It really isn't, especially when you try to explain it to somebody else.
It's difficult especially if you're not disciplined in the physics behind it. If you are, you can't communicate well with those who are not. I'm not, hence getting those who are to "normal speak" is a challenge. Understanding or rather envisioning the physical event and explaining it intelligently are almost impossible. So, here's the ignorant version
We tend to understand Newtonian concepts of fluids. We stir a beaker or bowl with water in it, it forms a bunch of circles where the mass shears..forms its layers ..faster in the spindle area ..slower as it moves outward. If it's too thick the stuff might just climb the spindle and leave a static mass outside of that immediate zone. If it's cooled more or of a slightly different property, it might just fracture and not remain a liquid at all and have a wad of gel spinning around on it. That's the non-Newtonian realm that we're dealing with when we're looking at cold properties.
..but make no mistake about it. a 5w-40 is always thicker/heavier than a 5w-20. It's not like you get some free ride up to operating temps.
For lack of full grasp of the physics involved, I would merely tell anyone to understand that like terms (5w-20 vs. 5w-40 for example) merely means that it "will pump" at the respective temps noted (-35F or whatever). It won't mean anything beyond that. No "same time to pressure" or anything like that. No "just as easy" in terms of rational flow (my term).
Here is a graph to illustrate the concept. It is not to any scale. A real graph would be nice, but I don't have one.
Click image for the whole sketch.
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Click image for the whole sketch.
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Originally Posted By: Gary Allan
Originally Posted By: Samilcar
Originally Posted By: Gary Allan
It's not really an intuitive concept.
It really isn't, especially when you try to explain it to somebody else.
It's difficult especially if you're not disciplined in the physics behind it. If you are, you can't communicate well with those who are not. I'm not, hence getting those who are to "normal speak" is a challenge. Understanding or rather envisioning the physical event and explaining it intelligently are almost impossible. So, here's the ignorant version
We tend to understand Newtonian concepts of fluids. We stir a beaker or bowl with water in it, it forms a bunch of circles where the mass shears..forms its layers ..faster in the spindle area ..slower as it moves outward. If it's too thick the stuff might just climb the spindle and leave a static mass outside of that immediate zone. If it's cooled more or of a slightly different property, it might just fracture and not remain a liquid at all and have a wad of gel spinning around on it. That's the non-Newtonian realm that we're dealing with when we're looking at cold properties.
..but make no mistake about it. a 5w-40 is always thicker/heavier than a 5w-20. It's not like you get some free ride up to operating temps.
For lack of full grasp of the physics involved, I would merely tell anyone to understand that like terms (5w-20 vs. 5w-40 for example) merely means that it "will pump" at the respective temps noted (-35F or whatever). It won't mean anything beyond that. No "same time to pressure" or anything like that. No "just as easy" in terms of rational flow (my term).
I understand it easily.
5W "5" Weight when Cold. Nice and Thin.. its Oil NOT WATER so it can Pour.. and again, its NOT WATER so its thin, liquid Dino Crude (or not) .. Oil. -5W.- COLD. Now, let us go to Step 2.
Enter HEAT. Oil Moving. Nice and thin, so that it can "Beat" the Cold and Flow. Now HEAT is applying.. it EXPANDS. its not WATER.. but it still EXPANDS!!! Like filling a Straw, a garden Hose when More Water is run through it. It gets "Bigger." So "30" is its "Weight" at its "Bigger" and "Hotter" Size.. its Oil NOT WATER, so it stays together.
This is made a "Film."
I hope i could help Illustrate.. I never thought about it in Inverse terms, and i suppose i could mentally flip it.. but Cold = Thin, Hot = Bigger (heat.)
Thanks.
Originally Posted By: Samilcar
Originally Posted By: Gary Allan
It's not really an intuitive concept.
It really isn't, especially when you try to explain it to somebody else.
It's difficult especially if you're not disciplined in the physics behind it. If you are, you can't communicate well with those who are not. I'm not, hence getting those who are to "normal speak" is a challenge. Understanding or rather envisioning the physical event and explaining it intelligently are almost impossible. So, here's the ignorant version
We tend to understand Newtonian concepts of fluids. We stir a beaker or bowl with water in it, it forms a bunch of circles where the mass shears..forms its layers ..faster in the spindle area ..slower as it moves outward. If it's too thick the stuff might just climb the spindle and leave a static mass outside of that immediate zone. If it's cooled more or of a slightly different property, it might just fracture and not remain a liquid at all and have a wad of gel spinning around on it. That's the non-Newtonian realm that we're dealing with when we're looking at cold properties.
..but make no mistake about it. a 5w-40 is always thicker/heavier than a 5w-20. It's not like you get some free ride up to operating temps.
For lack of full grasp of the physics involved, I would merely tell anyone to understand that like terms (5w-20 vs. 5w-40 for example) merely means that it "will pump" at the respective temps noted (-35F or whatever). It won't mean anything beyond that. No "same time to pressure" or anything like that. No "just as easy" in terms of rational flow (my term).
I understand it easily.
5W "5" Weight when Cold. Nice and Thin.. its Oil NOT WATER so it can Pour.. and again, its NOT WATER so its thin, liquid Dino Crude (or not) .. Oil. -5W.- COLD. Now, let us go to Step 2.
Enter HEAT. Oil Moving. Nice and thin, so that it can "Beat" the Cold and Flow. Now HEAT is applying.. it EXPANDS. its not WATER.. but it still EXPANDS!!! Like filling a Straw, a garden Hose when More Water is run through it. It gets "Bigger." So "30" is its "Weight" at its "Bigger" and "Hotter" Size.. its Oil NOT WATER, so it stays together.
This is made a "Film."
I hope i could help Illustrate.. I never thought about it in Inverse terms, and i suppose i could mentally flip it.. but Cold = Thin, Hot = Bigger (heat.)
Thanks.
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Quote:
5W "5" Weight when Cold. Nice and Thin.
No. It's like Motor Honey @ -30. It's just pumpable motor honey instead of a solid gelatinous mass like a SAE 30 would be.
5W "5" Weight when Cold. Nice and Thin.
No. It's like Motor Honey @ -30. It's just pumpable motor honey instead of a solid gelatinous mass like a SAE 30 would be.
Originally Posted By: Gary Allan
Quote:
5W "5" Weight when Cold. Nice and Thin.
No. It's like Motor Honey @ -30. It's just pumpable motor honey instead of a solid gelatinous mass like a SAE 30 would be.
Motor Honey.. Niice. I thought Lucas "Oil Stabilizer" (Useless, stupid?) Poured like Maple Syrup.
I know it will pour with not bad flow at 30 degrees and 20 degrees, not -30. That would be like you NEEDED 0W, right? -- Would the Car even START that cold, wouldnt the Gas freeze?
Quote:
5W "5" Weight when Cold. Nice and Thin.
No. It's like Motor Honey @ -30. It's just pumpable motor honey instead of a solid gelatinous mass like a SAE 30 would be.
Motor Honey.. Niice. I thought Lucas "Oil Stabilizer" (Useless, stupid?) Poured like Maple Syrup.
I know it will pour with not bad flow at 30 degrees and 20 degrees, not -30. That would be like you NEEDED 0W, right? -- Would the Car even START that cold, wouldnt the Gas freeze?
Originally Posted By: JCCADILLACMOBILE
Originally Posted By: Gary Allan
Quote:
5W "5" Weight when Cold. Nice and Thin.
No. It's like Motor Honey @ -30. It's just pumpable motor honey instead of a solid gelatinous mass like a SAE 30 would be.
Motor Honey.. Niice. I thought Lucas "Oil Stabilizer" (Useless, stupid?) Poured like Maple Syrup.
I know it will pour with not bad flow at 30 degrees and 20 degrees, not -30. That would be like you NEEDED 0W, right? -- Would the Car even START that cold, wouldnt the Gas freeze?
No the gas would not freeze. Water in the gas would freeze though.
Originally Posted By: Gary Allan
Quote:
5W "5" Weight when Cold. Nice and Thin.
No. It's like Motor Honey @ -30. It's just pumpable motor honey instead of a solid gelatinous mass like a SAE 30 would be.
Motor Honey.. Niice. I thought Lucas "Oil Stabilizer" (Useless, stupid?) Poured like Maple Syrup.
I know it will pour with not bad flow at 30 degrees and 20 degrees, not -30. That would be like you NEEDED 0W, right? -- Would the Car even START that cold, wouldnt the Gas freeze?
No the gas would not freeze. Water in the gas would freeze though.
When cold, the oil is too thick, so the engineer has "improved" the viscosity with polymers, and has chemically manipulated the oil by adding hydrogen molecules, so that it will flow more easily. the resultant "product" is the "multiviscosity" oil you refer to. it has improved ability to flow when cold, but is still thick enough when hot to maintain a film over the moving parts. the oil is still too thick when cold, but at least not as thick as it would be without the engineering added to it.
thanks to this improvement in oil technology, 5w30 oils are routinely recommended, and this contributes to vastly superior engine life span.
thanks to this improvement in oil technology, 5w30 oils are routinely recommended, and this contributes to vastly superior engine life span.
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Originally Posted By: crinkles
just google SAE J300 for the full definitions...
The definitions are static spec's. They don't rationalize the physical events in a sensible manner. Again, you need to be, more or less, disciplined in the physics (plebe level perhaps, for many here) to understand the terms.
The poise (symbol P; pronounced /ˈpwɑːz/) is the unit of dynamic viscosity in the centimetre gram second system of units. It is named after Jean Louis Marie Poiseuille.
1 P = 1 g·cm−1·s−1
The analogous unit in the International System of Units is the pascal second (Pa·s):
1 Pa·s = 1 kg·m−1·s−1 = 10 P
The poise is often used with the metric prefix centi-. A centipoise is one one-hundredth of a poise, and one millipascal-second (mPa·s) in SI units. (1 cP = 10−2P = 10−3 Pa·s) Centipoise is properly abbreviated cP, but the alternate abbreviations cps, cp, and cPs are also commonly seen.
Water has a viscosity of 0.0091 poise at 25 °C, or 1 centipoise at 20 °C.
Now rationalize that for someone who is limited to understanding PSI/gpm/l/m/lb/^2" ..etc.. ..and then integrate it in describing a physically visualized event.
Here's where everyone is lost. You need to go through too much fundamental orientation to get there. Each and every descriptive term above is not commonly understood "as stated".
It's a byproduct of the socialization that tends to occur in higher education. You've been educated singing to the preacher ..not preaching to your former peers. No one talks like that.
If I had time to make it through this learning curve, I'd be able to "speak" this in a 100% simple manner, since that was where I started in curiosity. Eventually a light bulb would turn on and everything would fit.
just google SAE J300 for the full definitions...
The definitions are static spec's. They don't rationalize the physical events in a sensible manner. Again, you need to be, more or less, disciplined in the physics (plebe level perhaps, for many here) to understand the terms.
The poise (symbol P; pronounced /ˈpwɑːz/) is the unit of dynamic viscosity in the centimetre gram second system of units. It is named after Jean Louis Marie Poiseuille.
1 P = 1 g·cm−1·s−1
The analogous unit in the International System of Units is the pascal second (Pa·s):
1 Pa·s = 1 kg·m−1·s−1 = 10 P
The poise is often used with the metric prefix centi-. A centipoise is one one-hundredth of a poise, and one millipascal-second (mPa·s) in SI units. (1 cP = 10−2P = 10−3 Pa·s) Centipoise is properly abbreviated cP, but the alternate abbreviations cps, cp, and cPs are also commonly seen.
Water has a viscosity of 0.0091 poise at 25 °C, or 1 centipoise at 20 °C.
Now rationalize that for someone who is limited to understanding PSI/gpm/l/m/lb/^2" ..etc.. ..and then integrate it in describing a physically visualized event.
Here's where everyone is lost. You need to go through too much fundamental orientation to get there. Each and every descriptive term above is not commonly understood "as stated".
It's a byproduct of the socialization that tends to occur in higher education. You've been educated singing to the preacher ..not preaching to your former peers. No one talks like that.
If I had time to make it through this learning curve, I'd be able to "speak" this in a 100% simple manner, since that was where I started in curiosity. Eventually a light bulb would turn on and everything would fit.
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