dumb oil question

[gamorg02]

ok so i corrected myself today in that a 15w-40 weight oil has a viscosity of '15' (yes i know thats arbitrary) in cold (Winter) temps. that is that its more fluid to help cold starting. its 40 weight when its warmed up, more viscous and less 'fluid'.

that being said, how come we warm our oil up before we change it. shouldn't it 'flow' better and drain better when its less viscious and colder?

what am i missing?

 

[ninjaneer]

To help me express my rather novice understanding, let's use 10W30 as an example. So here's what I understand: Oil doesn't really thicken (turning from 10 to 30 weight) as its internal temp increases. On the contrary--so when the oil is cold, it has the viscosity of a cold 10W, single weight, right. the thing is, as it warms up, it just doesn't thin as fast as a 10W (single-weight) oil would; and once it is up to to the spec'd temp, it has the viscosity of a 30W, single-weight oil supposedly would at that specified temp. In short, 10w30 only means that it should never act thinner than 10 or heaver than 30. So with "oil doesn't really thicken with heat" being said, the contrary isn't as so limited--all oils do thin out somewhat as they warm up. It still thickens as it gets colder and thins as it gets hotter, albeit just not as much.

 

[DMAN999]

An easy way to see why we warm our Bikes up a bit before changing the Oil is to go and see how the Oil Drains without warming it vs with it warmed up.
You can test this very easily in your own garage.
But as stated above Oil absolutely Flows/Drains better warm than cold.

 

[ninjaneer]

To help me express my rather novice understanding, let's use 10W30 as an example. So here's what I understand: Oil doesn't really thicken (turning from 10 to 30 weight) as its internal temp increases. On the contrary--so when the oil is cold, it has the viscosity of a cold 10W, single weight, right. the thing is, as it warms up, it just doesn't thin as fast as a 10W (single-weight) oil would; and once it is up to to the spec'd temp, it has the viscosity of a 30W, single-weight oil supposedly would at that specified temp. In short, 10w30 only means that it should never act thinner than 10 or heaver than 30. So with "oil doesn't really thicken with heat" being said, the contrary isn't as so limited--all oils do thin out somewhat as they warm up. It still thickens as it gets colder and thins as it gets hotter, albeit just not as much.

I guess more simply put, 10W30 means that, although the oil will still thicken as it gets colder, it won't get as thick as 30-straight would at the low end of the temp scale; and it'll still thin out with increased temps, just not as thin as 10-straight would at the high end.

 

[gamorg02]

To help me express my rather novice understanding, let's use 10W30 as an example. So here's what I understand: Oil doesn't really thicken (turning from 10 to 30 weight) as its internal temp increases. On the contrary--so when the oil is cold, it has the viscosity of a cold 10W, single weight, right. the thing is, as it warms up, it just doesn't thin as fast as a 10W (single-weight) oil would; and once it is up to to the spec'd temp, it has the viscosity of a 30W, single-weight oil supposedly would at that specified temp. In short, 10w30 only means that it should never act thinner than 10 or heaver than 30. So with "oil doesn't really thicken with heat" being said, the contrary isn't as so limited--all oils do thin out somewhat as they warm up. It still thickens as it gets colder and thins as it gets hotter, albeit just not as much.

correct me if i'm wrong here but those numbers means it sits between 5w and 15w cold and 20/40 when warm by these charts here:

http://www.upmpg.com/tech_articles/motoroil_viscosity/

An easy way to see why we warm aour Bikes up a bit before changing the Oil is to go and see how the Oil Drains without warming it vs with it warmed up.
You can test this very easily in your own garage.
But as stated above Oil absolutely Flows/Drains better warm than cold.

i 100% agree, but i'm just curious why with the above knowledge it seems like the opposite would be true?

 

[DMAN999]

I read that too, but all I know is that Warm Oil Flows out of an engine better than Cold Oil.
Read this (from here http://www.examiner.com/article/oil-viscosity-explained):

From this explanation, we can now gather some understanding about a bottle of oil by looking at the numbers. Using 10W-30 as an example, we can determine that at an oil temperature of 0 degrees Fahrenheit, the oil has the properties of 10 weight motor oil while at an oil temperature of 210 degrees Fahrenheit, the oil has the properties of 30 weight motor oil. This multi-viscosity behavior is achieved through the use of a viscosity modifier additive in the oil. The additive is dormant at cold temperatures but as the oil warms up, the modifier produces a thickening effect.

My guess is that since we don't run the Bike until it reaches the required temp for the Viscosity Modifiers in the Oil to Activate (and supossedly Thicken the Oil), it flows better at the moderate Temperature we do reach before draining it.
I usually run mine for about 5 Minutes (about halfway to operating temp) before draining it, I never get it so hot it could burn me.

But even at Full Operating Temps, I would expect the Oil to Flow even better than when simply Warm.

 

[ninjaneer]

hahahaha you guys! we all know what the truth is. i guess this is an exercise in understanding what is truly meant by the viscosity numbers. do you disagree with my post #4?

I guess more simply put, 10W30 means that, although the oil will still thicken as it gets colder, it won't get as thick as 30-straight would at the low end of the temp scale; and it'll still thin out with increased temps, just not as thin as 10-straight would at the high end.

 

[sdt354]

I always questioned that myself Garrett. I still don't believe they can make oil do that! Cold, the gauge is pegged, hot 5psi?

Steve

correct me if i'm wrong here but those numbers means it sits between 5w and 15w cold and 20/40 when warm by these charts here:

http://www.upmpg.com/tech_articles/motoroil_viscosity/



i 100% agree, but i'm just curious why with the above knowledge it seems like the opposite would be true?

 

[gamorg02]

hahahaha you guys! we all know what the truth is. i guess this is an exercise in understanding what is truly meant by the viscosity numbers. do you disagree with my post #4?

i sort of do (by reading not by what i've actually noted in real life which contradicts all this):

if you look at the charts 15w is: 4.1, which I assume is some sort of 'time' for it to get through an orafice at 0?. however 40(non-w) is 12.5. that means to me that the 15w in cold weather is 3x more viscious! it makes no sense!!!

 

[RaWarrior]

From howstuffworks.com

Multi viscosity oils work like this: Polymers are added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.

So ninjaneer has the right idea. The 10 weight oil does not suddenly turn into 40 weight when it gets hot. Viscosity is inverse to temperature, as in higher temp= lower viscosity. So a hot 40w is still thinner than a cold 10w, but not as thin as a hot 10w.

The idea behind running an engine before changing the oil was also to stir up and sediment that may have settled in crevices to suspend it in the oil so it will drain out rather than remain in the engine and immediately contaminate the new oil.

 

[Lew L]

Just to add a bit to the mix:

Motor oil "Falls out of grade" as the miles pile up. After 2,000 miles a 10W40 oil will measure out to 10W 20 or 10W30. The polymer that is the "viscoity improver" get cut into smaller pieces by the transmission gears and the oil cannot maintain its viscosity.

 

[bazwell]

From howstuffworks.com

Multi viscosity oils work like this: Polymers are added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.

So ninjaneer has the right idea. The 10 weight oil does not suddenly turn into 40 weight when it gets hot. Viscosity is inverse to temperature, as in higher temp= lower viscosity. So a hot 40w is still thinner than a cold 10w, but not as thin as a hot 10w.

The idea behind running an engine before changing the oil was also to stir up and sediment that may have settled in crevices to suspend it in the oil so it will drain out rather than remain in the engine and immediately contaminate the new oil.

That learned me good! :biglaugh:

So, why don't people vanish into fat air? Riddle me THAT one Batman!

 

[gamorg02]

So ninjaneer has the right idea. The 10 weight oil does not suddenly turn into 40 weight when it gets hot. Viscosity is inverse to temperature, as in higher temp= lower viscosity. So a hot 40w is still thinner than a cold 10w, but not as thin as a hot 10w.

not sure i agree with that. does your w's mean 40weight oil or a 40winter oil?