Oil 101 - Revised and Expanded Chapter 1

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Originally Posted By: Solarent
I think it is time to update Motor Oil 101. It gets quoted a lot and has helped many people begin to understand some of the basics. Without getting too technical I’ve followed the same general format, but re-written the topics so it is more accurate.
No disrespect to AE Haas, his article has helped many and will continue to do so.
I welcome your comments and input and hopefully if this ends up replacing the current Motor Oil University, the powers that be at BITOG will also take them into consideration.



Chapter One – Operating Temperatures and Viscosity
Understanding what viscosity grades mean can be confusing. The average driver just tries to follow what is in the owners manual – this is a good practice. Some owners manuals allow for different grades for example 0W30 synthetic or 5W30 mineral oil. Others may have a chart which gives recommendations based on the ambient temperatures, and newer engines are recommending even lighter grade oils because there are fuel economy advantages to doing so.

In this chapter we aren’t going to talk about viscosity grades – that will be in chapter 2. In this chapter we will talk about some basic principles of viscosity and how it relates to your engine. For the purposes of this chapter we will talk about viscosity in the unit it is most often measured centistokes (cSt). You don’t have to worry about what that means, but cSt are different from the SAE viscosity grade. For now let’s focus on the basics.

Viscosity is a fluid’s (gas or liquid) resistance to flow. A high viscosity fluid (like molasses) is thick and doesn’t flow easily. A low viscosity fluid (like water) is thin and flows much more easily. For most liquids, the flow rate changes as the temperature of the liquid changes. In engine oil, hot oil has a lower viscosity and flows more easily than cold oil. This is important because your engine – and the oil that is in it runs at a range of temperatures from start up, through the warm up period and at operating temperature.
In the early days of the automobile, engine oils were very simple, basic refined fluids that helped keep moving parts easily sliding past each other. Different oils had different flow rates and there was a very simple way to reference their flow rates relative to each other. Each range of flow rates was assigned a numerical grade. Over time various additives were put into engine oils to allow them to do different things, like changing the flow rate as the temperature changed. Because of these changes the grading system also was changed. But we will talk about that more later.

For now let’s just focus on what happens to a basic oil as the temperature changes. Sometimes confusion occurs because people think in terms of the oil thinning when it gets hot. They think this thinning with heat is the problem with motor oil. It would be more correct to think that oil thickens when it cools to room temperature and THIS is the problem. It is said that 90 percent of engine wear occurs at startup. If we are interested in engine longevity then we should concentrate our attention at reducing engine wear at startup.

Oils recommended by the engine manufacturer is primarily based on giving the right thickness at the normal operating temperature. So let’s focus on that. As an example: If the normal operating temperature is 212F (100C) and the engine needs to operate with an oil viscosity of 10 cSt based on the manual recommendation; then what does that mean for the engine oil at startup when the engine isn’t at 212F? What about during the warm up period? What happens to the oil then? In an ideal world the engine oil viscosity would always be 10 cSt, however in real world terms, the oil thickens as the temperature decreases. If fact, a basic mineral oil thickens so much that it won’t lubricate the engine properly at all. If the oil is 10 cSt at 212F, then at 104F (40C) it thickens up to 100 cSt, and at 32F (0C) to 250cSt and so on. The oil becomes so thick at start-up temperatures that the engine might not even start. There is also real wear that can happen and the engine could break down.

So the easy way to fix this is to just have the oil be 10cSt at startup right? After all if the right viscosity for the engine to operate is 10cSt why not just start there and let it be? The engine would be properly lubricated and no harm. The problem is that if you started at 10cSt then as the engine gets hotter (which they do) then your oil would be much to thin when the engine gets up to operating temperature.
So what do you do – engines have a wide range of start-up temperatures – which even change as the seasons change. How do you get the right operating temperature viscosity when the start-up temperatures are so widely different? In the old days you would use a thicker oil in the summer and a thinner oil in the winter. Today with pressurized water cooled engines, the engine blocks run close to the same operating temperature all year round. As the engine warms up to that temperature the oil starts out too thick and slowly thins out as the temperature increases. This is very inefficient and causes the engine to waste energy slogging through oil that is too thick.

So what you need the right operating temperature viscosity with the flexibility of different startup temperatures you need oil that either doesn’t thicken too much as the temperature decreases and doesn’t thin out too much as the temperature increases. Ideally being as close to 10cSt at start up and then staying close to 10 cSt throughout warm up and up to operating temperature. It won’t be possible to be 10cSt at every temperature, but if we could at least be closer at the colder temperatures that would be better right? So the industry invented an oil that does just that, and called it a multi-grade oil.
 
good job Sol.
thumbsup2.gif
 
Quote:
If fact, a basic mineral oil thickens so much that it won’t lubricate the engine properly at all. If the oil is 10 cSt at 212F, then at 104F (40C) it thickens up to 100 cSt, and at 32F (0C) to 250cSt and so on. The oil becomes so thick at start-up temperatures that the engine might not even start. There is also real wear that can happen and the engine could break down.


I think this part needs rephrasing, or clarification. A 100 cSt oil isn't gong to cause harm, nor a 250 cSt oil, but this makes it sound like it will. In fact, at those temperatures the engine is really relying on that high viscosity to keep from wearing. I don't think you'd want to cause a panic if those readers see an SAE J300 chart after this?

Other than that, a good introduction!
 
I didn't want to depart too far from the original text here, but you may be right. Any suggestions on how to better clarify?

What about something like replacing the last sentence with: "Of course the oil you buy isn't going to be as basic as this and will be adjusted by the oil maker to avoid these issues, but it's just an example to show you what happens to oil as the temperature drops - and the potential for real wear that could happen which eventually might cause the engine to break down"
 
Leave the first 2 sentences but change the last 2.

Well, you could say (I'm not native english so might need some rephrasing):

When it gets really cold, colder than what the oil was intended for, the oil becomes so thick at start-up temperatures that the engine might not even start. There is also real wear that can happen and the engine could break down if it does start.
 
So the new paragraph would read:

Quote:
In fact, a basic mineral oil thickens so much that it won’t lubricate the engine properly at all. If the oil is 10 cSt at 212F, then at 104F (40C) it thickens up to 100 cSt, and at 32F (0C) to 250cSt and so on. When it gets really cold, colder than what the oil was intended for, the oil could become so thick at start-up temperatures that the engine might not even start. There is also real wear that can happen and the engine could break down if it does start.


I am ok with this change - If it ends up as a main page article, hopefully the editors will make the adjustment. Thank you for your input!
 
Solarent, thanks for taking the initiative, it's a good one.

Originally Posted By: Solarent
So the new paragraph would read:

Quote:
In fact, a basic mineral oil thickens so much that it won’t lubricate the engine properly at all. If the oil is 10 cSt at 212F, then at 104F (40C) it thickens up to 100 cSt, and at 32F (0C) to 250cSt and so on. When it gets really cold, colder than what the oil was intended for, the oil could become so thick at start-up temperatures that the engine might not even start. There is also real wear that can happen and the engine could break down if it does start.


I am ok with this change - If it ends up as a main page article, hopefully the editors will make the adjustment. Thank you for your input!


How about

Quote:
In fact, a basic mineral oil can thicken so much that it won’t lubricate the engine properly at all. If the oil is 10 cSt at 212F, then at 104F (40C) it thickens up to 100 cSt, and at 32F (0C) to 250cSt and so on. This gets increasingly worse as the temperatures get colder, and at the low temperature limit for a particular oil, when it gets really cold, it can be over 1,000 times thicker than at operating temperature. At this point, the engine might not even start. If it does, the oil might not be able to be pumped into the areas that require it, which can cause more wear, or even lead to failure in minutes.


As to the premise that an ideal oil would start at 10, this would require the additives to be fully functional at start temperature...in the early period, the "overly" think period keeps the parts apart before you get into the boundary/mixed regimes as the oil warms.
 
I don't agree with this statement "Oils recommended by the engine manufacturer is primarily based on giving the right thickness at the normal operating temperature."

Normal operating temperature of most high performance German vehicles is around 100C most of the times. But if someone floors their gas pedal of a BMW M3 on autobahn or on Nurburgring for more than 20-30 minutes the oil temp will be much higher than 100C. The oil BMW, MB, Audi ... recommended are for these conditions. I am very sure that xW40 at 130-140C is thinner than xW20 at 100C.

In America it is almost impossible to redline a car for longer than few seconds on public roads, only a handful of drivers track their cars and those drivers should use appropriate oil for their special conditions.

Also, where the car is operated many need thicker or thinner oil. Same car, one is in Alaska from November to April and driven mostly under 2-3 miles and the other is in Phoenix from May to October driven more than 50-60 miles a trip, these two identical cars may need different oil grade.
 
Last edited:
Please read, I re-wrote some of this ...

Originally Posted By: Solarent

Chapter One – Operating Temperatures and Viscosity
Understanding what viscosity grades mean can be confusing. The average driver just tries to follow what is in the owners manual – this is a good practice. Some owners manuals allow for different grades for example 0W30 synthetic or 5W30 mineral oil. Others may have a chart which gives recommendations based on the ambient temperatures range locally. And newer engines with improved manufacturing techniques are recommending even lighter grade oils because there are fuel economy advantages to doing so.

In this chapter we are not going to talk about viscosity grades – that will be in chapter 2.

In this chapter we will talk about some basic principles of viscosity and how it relates to your engine. For the purposes of this chapter we will talk about viscosity in the unit it is most often measured centistokes (cSt). You don’t have to worry about what that means, but cSt are different from the SAE viscosity grade. For now let’s focus on the basics.

Viscosity is a fluid’s (gas or liquid) resistance to flow. A high viscosity fluid (like molasses) is thick and doesn’t flow easily. A low viscosity fluid (like water) is thin and flows much more easily. For most liquids, the flow rate changes as the temperature of the liquid changes. In engine oil, hot oil has a lower viscosity and flows more easily than cold oil. This is important because your engine – and the oil that is in it runs at a range of temperatures from start up, through the warm up period and at operating temperature.

In the early days of the automobile, engine oils were very simple, basic refined fluids that helped keep moving parts easily sliding past each other. Different oils had different flow rates and there was a very simple way to reference their flow rates relative to each other. Each range of flow rates was assigned a letter; A, B, C were different "weights" of oil - or thicknesses. Around WW-II the Society of Automotive Engineers ( SAE ) devised a numerical system that would allow a wider range of viscosities to be described based on numbers. We use a variant of this system today.

Over time various additives were put into engine oils to allow them to do different things, like changing the flow rate as the temperature changed. Because of these changes the grading system also was enhanced. But we will talk about that more later.

For now let’s just focus on what happens to a basic oil as the temperature changes. Sometimes confusion occurs because people think in terms of the oil thinning when it gets hot. They think this thinning with heat is the problem with motor oil - and it might be if we get way to hot. But in a properly running motor this does not happen. However, it would be more correct to think that oil thickens when it cools to ambient temperature.

It is said that 90 percent of engine wear occurs at startup. If we are interested in engine longevity then we should concentrate our attention at reducing engine wear at startup. This means maintaining a robust lubricating film on cool surfaces and keeping parts separate when they are trying to collide. Cool thick oil does just that, as long as it's not too thick.

But, if the oil gets too cold, it gels and sometimes separates. In this state, it can not keep up with reciprocating parts moving at speeds of hundreds or thousands of feet per second and it fails. The parts come together and wear occurs.

The other thing that happens in cold engines is that the by-products of combustion (H2O) condense on cool or cold surfaces like cold iron cylinder walls. So you have a water film fighting and oil film while the piston rings are scraping both toward the crankcase. This leads to upper cylinder wear and is the biggest source of wear on cold start. Some of the oil additives are directed at reducing this wear.

Oil recommended by the engine manufacturer is primarily based on giving the right thickness at the normal operating temperature. So let’s focus on that. As an example: If the normal operating temperature is 50 to 212F (100C) and the engine needs to operate with an oil viscosity of 10 cSt under load based on the manual recommendation; then what does that mean for the engine oil at startup when the engine isn’t at 212F?

What about during the warm up period? What happens to the oil then? In an ideal world the engine oil viscosity would always be 10 cSt under load, however in real world terms, the oil thickens as the temperature decreases. If fact, a basic mineral oil thickens so much that it won’t lubricate the engine properly at all [Sorry B_S]. If the oil is 10 cSt at 212F, then at 104F (40C) it thickens up to 100 cSt, and at 32F (0C) to 250cSt and so on. If the wrong oil has been selected, the oil becomes so thick at start-up temperatures that the engine might not even start. There is also real wear that can happen and the engine could break down. So the cold lubrication factor is described by the first numerical listing in the oil grade selected by the design engineers - more on this in later chapters.

So the easy way to fix this is to just have the oil be 10cSt at startup right? After all if the right viscosity for the engine to operate is 10cSt why not just start there and let it be? The engine would be properly lubricated and no harm. The problem is that if you started at 10cSt then as the engine gets hotter (which they do) then your oil would be much to thin when the engine gets up to operating temperature.

So what do you do – engines have a wide range of start-up temperatures – which even change as the seasons change. How do you get the right operating temperature viscosity when the start-up temperatures are so widely different? In the old days you would use a thicker oil in the summer and a thinner oil in the winter. Today with pressurized water cooled engines, the engine blocks run close to the same operating temperature all year round. As the engine warms up to that temperature the oil starts out thick and slowly thins out as the temperature increases. The thick cold film protects the surfaces while the engine is warming up and when it gets to temperature it gets to work for many miles or hours well protected.

So what you need the right operating temperature viscosity with the flexibility of different startup temperatures you need oil that either doesn’t thicken too much as the temperature decreases and doesn’t thin out too much as the temperature increases. Ideally being as thick as needed to protect at start-up, while thinning reasonably quickly to the desired viscosity for hot running under load - say 10cSt. It won’t be possible to be 10cSt at every temperature, but if we could at least be closer at the colder temperatures that would be better right? So the industry invented an oil that does just that, and called it a multi-grade oil.



Sorry, but I had to take a shot at re-write. I know it's not polished. We'll have to tweak it. But see if it is going the right way? Please read and ponder the re-write to see if it makes a better case?

We need to speak truth if possible. I think we can. You are doing yeoman work by putting this together. Please keep going
smile.gif
 
Last edited:
Thank you for your input.

For ease in editing I suggest that you highlight your changes in another color. This way it can easily be identified
 
Understood, but BITOG won't allow edits past a few minutes after posting so I can't go back and do as requested ... Sorry, you'll have to do a compare in Word or something ...
 
Originally Posted By: BrocLuno
Please read, I re-wrote some of this ...

Originally Posted By: Solarent

Chapter One – Operating Temperatures and Viscosity
Understanding what viscosity grades mean can be confusing. The average driver just tries to follow what is in the owners manual – this is a good practice. Some owners manuals allow for different grades for example 0W30 synthetic or 5W30 mineral oil. Others may have a chart which gives recommendations based on the ambient temperatures range locally. And newer engines with improved manufacturing techniques are recommending even lighter grade oils because there are fuel economy advantages to doing so.

In this chapter we are not going to talk about viscosity grades – that will be in chapter 2.

In this chapter we will talk about some basic principles of viscosity and how it relates to your engine. For the purposes of this chapter we will talk about viscosity in the unit it is most often measured centistokes (cSt). You don’t have to worry about what that means, but cSt are different from the SAE viscosity grade. For now let’s focus on the basics.

Viscosity is a fluid’s (gas or liquid) resistance to flow. A high viscosity fluid (like molasses) is thick and doesn’t flow easily. A low viscosity fluid (like water) is thin and flows much more easily. For most liquids, the flow rate changes as the temperature of the liquid changes. In engine oil, hot oil has a lower viscosity and flows more easily than cold oil. This is important because your engine – and the oil that is in it runs over range of temperatures from start up, through the warm up period and on to operating temperature.

In the early days of the automobile, engine oils were very simple, basic refined fluids that helped keep moving parts easily sliding past each other. Different oils had different flow rates and there was a very simple way to reference their flow rates relative to each other. Each range of flow rates was assigned a letter; A, B, C were different "weights" of oil - or thicknesses. Around WW-II the Society of Automotive Engineers ( SAE ) devised a numerical system that would allow a wider range of viscosities to be described based on numbers. We use a variant of this system today.

Over time, as oil chemistry advanced, various additives were put into engine oils to allow them to do different things, like changing the flow rate as the temperature changed. Because of these changes the grading system also was enhanced.
But we will talk about that more later.

For now let’s just focus on what happens to a basic oil as the temperature changes. Sometimes confusion occurs because people think in terms of the oil thinning when it gets hot. They think this thinning with heat is the problem with motor oil - and it might be if we get way too hot. But in a properly running motor this does not happen. It would be more correct to think that oil thickens when it cools to ambient temperature.

It is said that 90 percent of engine wear occurs at startup. If we are interested in engine longevity then we should concentrate our attention at reducing engine wear at startup. This means maintaining a robust lubricating film on cool surfaces and keeping parts separate when they are trying to collide. Cool thicker oil does just that, as long as it's not too thick.

But, if the oil gets too cold, it gels and sometimes separates. In this state, it can not keep up with reciprocating parts moving at speeds of hundreds or thousands of feet per second and it fails. The parts come together and wear occurs.

The other thing that happens in cold engines is that the by-products of combustion (H2O) condense on cool or cold surfaces like cold iron cylinder walls. So you have a water film fighting an oil film while the piston rings are scraping both toward the crankcase. This leads to upper cylinder wear and is the biggest source of wear on cold start. Some of the oil additives are directed at reducing this wear.


Oil recommended by the engine manufacturer is primarily based on giving the right thickness at the normal operating temperature. So let’s focus on that. As an example: If the normal operating temperature is 150 to 212F (100C) and the engine needs to operate with an oil viscosity of 10 cSt under load, based on engineering as shown the manual recommendation; then what does that mean for the engine oil at startup when the engine isn’t at 212F? What about during the warm up period? What happens to the oil then?

In an ideal world the engine oil viscosity would always be 10 cSt under load, however in real world terms, the oil thickens as the temperature decreases. If fact, a basic mineral oil thickens so much that it won’t lubricate the engine properly at all [Sorry B_S] unless you are describing gellation .... If the oil is 10 cSt at 212F, then at 104F (40C) it thickens up to 100 cSt, and at 32F (0C) to 250cSt and so on. If the wrong oil has been selected, the oil becomes so thick at start-up temperatures that the engine might not even start. There is also real wear that can happen and the engine could break down. So the cold lubrication factor is described by the first numerical listing in the oil grade selected by the design engineers - more on this in later chapters. [Above we say we are not going to go into viscosities and SAE descriptors ...]

So the easy way to fix this is to just have the oil be 10cSt at startup right? After all if the right viscosity for the engine to operate is 10cSt why not just start there and let it be? The engine would be properly lubricated and no harm. The problem is that if you started at 10cSt then as the engine gets hotter (which they do) then your oil would be much to thin when the engine gets up to operating temperature.

So what do you do – engines have a wide range of start-up temperatures – which even change as the seasons change. How do you get the right operating temperature viscosity when the start-up temperatures are so widely different? In the old days you would use a thicker oil in the summer and a thinner oil in the winter. Today with pressurized water cooled engines, the engine blocks run close to the same operating temperature all year round. As the engine warms up to that temperature the oil starts out thick and slowly thins out as the temperature increases. The thick cold film protects the surfaces while the engine is warming up and when it gets to temperature it gets to work for many miles or hours well protected.

So what you need is the right operating temperature viscosity with the flexibility of different startup temperatures. You need oil that either doesn’t thicken too much as the temperature decreases and doesn’t thin out too much as the temperature increases. Ideally being as thick as needed to protect at start-up, while thinning reasonably quickly to the desired viscosity for hot running under load - say 10cSt. It won’t be possible to be 10cSt at every temperature, but if we could at least be closer at the colder temperatures that would be better right? So the industry invented an oil that does just that, and called it a multi-grade oil.



Sorry, but I had to take a shot at re-write. I know it's not polished. We'll have to tweak it. But see if it is going the right way? Please read and ponder the re-write to see if it makes a better case?

We need to speak truth if possible. I think we can. You are doing yeoman work by putting this together. Please keep going
smile.gif



OK, now colored in blue.
 
Some suggested changes:


Originally Posted By: Solarent



Chapter One – Operating Temperatures and Viscosity
Understanding what viscosity grades mean can be confusing. The average driver just tries to follow what is in the owners manual – this is a good practice. Some owners manuals allow for different grades based on the predicted operating temperature. For example, they may specify a 0W30 synthetic or a 5W30 mineral oil. Others may have a chart which gives recommendations based on the ambient temperatures. Newer vehicle manufacturers are recommending even lighter grade engine oils, because there are fuel economy advantages to doing so.

In this chapter we aren’t going to talk about viscosity grades – that will be in chapter 2. In this chapter we will talk about some basic principles of viscosity and how it relates to your engine. For the purposes of this chapter we will talk about viscosity in the unit it is most often measured in centistokes (cSt). You don’t have to worry about what that means, but cSt are different from the SAE viscosity grade. For now let’s focus on the basics.

Viscosity is a fluid’s (gas or liquid) resistance to flow. A high viscosity fluid (like molasses) is thick and doesn’t flow easily. A low viscosity fluid (like water) is thin and flows much more easily. For most liquids, the flow rate changes as the temperature of the liquid changes. In engine oil, hot oil has a lower viscosity and flows more easily than cold oil. This is important because your engine and the oil that is in it runs at a range of temperatures from start up up, through the warm up period, to the operating temperature.

In the early days of the automobile, engine oils were very simple, basic refined fluids that helped keep moving parts easily sliding past each other. Different oils had different flow rates and there was a very simple way to reference their flow rates relative to each other. Each range of flow rates was assigned a numerical grade. Over time various additives were put into engine oils to allow them to do different things, like changing the flow rate as the temperature changed. Because of these changes the grading system also was changed. But we will talk about that more later.

For now let’s just focus on what happens to a basic oil as the temperature changes. Sometimes confusion occurs because people think in terms of the oil thinning when it gets hot. They think this thinning with heat is the problem with motor oil. It would be more correct to think that oil thickens when it cools to room temperature and THIS is the problem. It is said that 90 percent of engine wear occurs at startup. If we are interested in engine longevity then we should concentrate our attention at reducing engine wear at startup.

Oils recommended by the engine manufacturer is primarily based on giving the right thickness at the normal operating temperature. So let’s focus on that. As an example: If the normal operating temperature is 212F (100C) and the engine needs to operate with an oil viscosity of 10 cSt based on the manual recommendation; then what does that mean for the engine oil at startup when the engine isn’t at 212F? What about during the warm up period? What happens to the oil then? In an ideal world the engine oil viscosity would always be 10 cSt, however in real world terms, the oil thickens as the temperature decreases. A basic, un-additized mineral oil could thicken so much that it won’t lubricate the engine properly at all. If the oil is 10 cSt at 212F, then at 104F (40C) it thickens up to 100 cSt, and at 32F (0C) to 250cSt and so on. The oil becomes so thick at start-up temperatures that the engine might not even start. There is also real wear that can happen and the engine could break down.

So the easy way to fix this is to just have the oil be 10cSt at startup right? After all if the right viscosity for the engine to operate is 10cSt why not just start there and let it be? The engine would be properly lubricated and no harm. The problem is that if you started at 10cSt then as the engine gets hotter (which they do), your oil would be much too thin when the engine gets up to operating temperature.

So what do you do – engines have a wide range of start-up temperatures – which even change as the seasons change. How do you get the right operating temperature viscosity when the start-up temperatures are so widely different? In the old days you would use a thicker oil in the summer and a thinner oil in the winter. Today with pressurized water cooled engines, the engine blocks run close to the same operating temperature all year round. As the engine warms up to that temperature the oil starts out too thick and slowly thins out as the temperature increases. This is very inefficient and causes the engine to waste energy slogging through oil that is too thick.

So what you need the right operating temperature viscosity with the flexibility of different startup temperatures you need oil that either doesn’t thicken too much as the temperature decreases and doesn’t thin out too much as the temperature increases. Ideally being as close to 10cSt at start up and then staying close to 10 cSt throughout warm up and up to operating temperature. It won’t be possible to be 10cSt at every temperature, but if we could at least be closer at the colder temperatures that would be better right? So the industry invented an oil that does just that, and called it a multi-grade oil.
 
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