Oil 101 - Revised and Expanded Chapter 2

[Solarent]

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 Two – Oil Grades In chapter one we talked about how oil changes viscosity as the temperature increases and the challenge it is to keep close to the right operational viscosity regardless of the temperature. If the operating temperature is 212F and the recommended viscosity is 10cSt then OIL A which can be made to be 40 cSt at 104F(40C) is going to be better than OIL B that is 100cSt at 104F (40C). They will still be both too thick at start up and during the warm up period but OIL A will flow better and waste less energy. So when you buy an oil at the store you will see on it a grade which will read something like 5W30. This grade is based on the way the viscosity changes to temperature and references a standard chart called the SAE J300. I won’t bore you with the details of how the chart has changed over the years, but I will tell you that as engines and oils have developed, the system has been updated to reflect the current way oils are selected by engine manufacturers and oil makers. The system isn’t perfect but it is used worldwide, so understanding the basics of how it works and how it relates to your engine oil viscosity can help a great deal. The engine oil grade is divided into 2 parts: XW and YY to make XWYY (the X and YY are replaced with numbers). I like to think of this as a school grade that is made up of 2 parts – attendance and participation. In order to get the best grades in school you have to both show up and participate. If you only show up then you the grade won’t be the best; if you only show up some of the time your grade also won’t be the best, and either way you may not meet the requirements to pass the class. It is the same with engine oil grades. If you want the best grade for your engine, you need both parts of the grade together to meet the requirements of the engine builder’s specification. Instead of attendance and participation, for engine oils we have cold temperature performance and high temperature performance. Like I said we need both in order to do well. So this combination of the two parts XW and YY is called a “multi-grade”. Each part of the engine oil grade is based on different tests and have a different numbering system. For the first part (the cold temperature performance) it is based on the flow rate and pumpability at cold temperatures (below 32F or 0C). Each section of the rating scale is based on a range of numbers scored on standardized cold temperature tests. Since winter is cold and it is a good way to remember it, the W is used to indicate that this number is from the cold rating scale. From the lightest viscosity to the heaviest the scale is as follows: 0W, 5W, 10W, 15W, 20W, 25W. The second part (the high temperature performance) is based on the viscosity rating at 212F (100C) and how the oil responds to high temperatures and something called shear forces – or HTHS – this is an important number that will be talked about in a future chapter. Each section of the rating scale is based on standardized high temperature tests. From the lightest viscosity to the heaviest the scale is as follows 8, 12, 16, 20, 30, 40, 50, 60. So for an engine oil grade you have a combination of the first part (cold temperature performance) and the second part (high temperature performance) for example 5W30. When comparing oils you can say that 0W30, 5W30, 10W30 all have similar high temperature performance, with a range in cold temperature performance options. Similarly you could compare 0W16, 0W20, 0W30 and 0W40 as all having similar cold temperature performance, but a range in high temperature performance. Do you remember our 10 cSt example oil from Chapter 1? This fluid fits on the high temperature performance scale at 30 so it is an XW30 oil. If we were to compare a 0W30 and a 10W30 they all fit into the same category for the high temperature performance. Some people think that a 0W30 is way too thin and that it won’t protect your engine – We’ve heard people say that Porsche specifically prohibits a 0W30 engine oil for that reason. In reality, at operating temperature they would be the same! The difference is at 75F, your startup temperature in the morning: 10W30 Thickness at 75F: 100 cSt Thickness at 212 F: 10 cSt --- 0W30 Thickness at 75F: 40 cSt Thickness at 212 F: 10 cSt Now you can see that the difference between the desired thickness your engine requires ( = 10 ) is closest to the 0W-30 oil at startup. It is still too thick for normal operation. But it does not have as far to go as the 10W30, before it warms up and thins to the correct viscosity. Remember that most engine wear occurs at startup when the oil is too thick to lubricate properly. Most of the thick oil at startup actually goes through the bypass valve back to the engine oil sump and not into your engine oil galleys where it is spread to various engine components. This is especially true when you really step on that gas pedal. You really need more lubrication and you actually get less. So how does this happen? How can you have 2 oils with different grades both meet the same high temperature performance, yet one is much closer to the correct viscosity at startup? The answer is in how the oil is made.

 

[MolaKule]

Good stuff Sol, keep it up.

 

[Jetronic]

Quote:

They will still be both too thick at start up and during the warm up period but OIL A will flow better and waste less energy.

Both oils flow the same, but the thicker oil will reguire (and get) more energy.

Quote:

The difference is at 75F

the difference is at temperatures below freezing. If there's a difference at 75F, it's due to a different viscosity index, but the winter grade has o bearing at such high temperatures.

Quote:

10W30 Thickness at 75F: 100 cSt Thickness at 212 F: 10 cSt --- 0W30 Thickness at 75F: 40 cSt Thickness at 212 F: 10 cSt

should be: 10W30 Thickness at -13F: 60,000 cSt Thickness at 212 F: 10 cSt --- 0W30 Thickness at -13F: 15,000 cSt Thickness at 212 F: 10 cSt

Quote:

Now you can see that the difference between the desired thickness your engine requires ( = 10 ) is closest to the 0W-30 oil at startup. It is still too thick for normal operation. But it does not have as far to go as the 10W30, before it warms up and thins to the correct viscosity. Remember that most engine wear occurs at startup when the oil is too thick to lubricate properly. Most of the thick oil at startup actually goes through the bypass valve back to the engine oil sump and not into your engine oil galleys where it is spread to various engine components. This is especially true when you really step on that gas pedal. You really need more lubrication and you actually get less.

This part misleading; the oil is only flowing through the bypas if the oil pressure is at it's maximum value, determined by the pressure relief valve. And even if that happens, the parts being pressure fed (bearings) get all the oil they need. Wear happens during warmup when the oilis thinning because of the rising temperature, but the antiu-wear chemistry isn't activated yet because the temperature isn't high enough yet.

 

[69GTX]

Remember that most engine wear occurs at startup when the oil is too thick to lubricate properly. Most wear occurs during the warmup phase to 165-175 deg F, even if the oil is flowing fine from the moment you turned the key. Maybe 5-10% occurs at startup....the other 90-95% during warmup to normal operating temperatures. Even if the oil is thick, if you are using the mfg's recommended grade of oil in the correct temperature range, then the residual droplets and pools of oil in the bearings and other components is normally enough lubrication until full system oil pressure is established.

 

[ryanm8]

The impression I get when reading this is that a 0wXX oil would always protect better than a 10wXX oil would. While true for extremely low temperatures, wouldn't the thicker oil protect better above ~0 deg. F until up to operating temp?

 

[Solarent]

Originally Posted By: ryanm8

The impression I get when reading this is that a 0wXX oil would always protect better than a 10wXX oil would. While true for extremely low temperatures, wouldn't the thicker oil protect better above ~0 deg. F until up to operating temp?

It's not that it would protect better, but rather that it would protect the same, but require less energy for pumping. This turns into improved fuel economy which is the main driver behind the lighter viscosity grades. This also is in reference to everyday uses of engine oil. More extreme applications may require appropriate adaptation.

 

[CT8]

Oil 101 has caused so many people to sound so uninformed when they regurgitate their new found wisdom the oil university.

 

[CT8]

[quote=69GTX] Remember that most engine wear occurs at startup when the oil is too thick to lubricate properly. How is the oil too cold to lubricate properly unless it is too cold to pump? The time it takes for the oil to travel from the sump to the pump is the most important factor . That is why it is so important to choose the proper xW viscosity for the starting temps. Cold engine clearances are looser than when at operating temps, There is more wear the looser the clearances are. To start and run when cold the fuel mixture needs to be richer and there is less vaporization of the air fuel mixture so the fuel washes down the oil from the cylinder walls and the condensation is greater[more wear] and poor combustion. Remember the oval pistons and clearances in a cold engine means much more blow by. looking at a worn engine you will notice the wear on the cylinder is mostly at top dead center where the piston speed is the lowest and the oil film the thinnest and the pressures and combustion pressures the highest.Recall the cold start wash down from the richer mixture. The oil film is minimal at starting at the crank,rod and cam bearings until full flow is achieved and the parts are separated by the oil [more wear] the parts can even be touching, look at the wear patterns on the crankshaft and rod bearings. The basic and most important duty of oil is to keep the parts separated. Any one water ski? Once the engine is running and stabilized the oil additives that work when heated come into play. Only then the engine wear depending on how the engine is operated is minimal.

 

[weasley]

ZDDP doesn't start working until it gets warm, so when cold you are relying mostly on hydrodynamic protection (or any other surface-active agents). The oil pump is a positive displacement design, so it will pump the same amount of oil regardless of the viscosity (within reasonable boundaries). If the pump is turning at xxx rpm, it will pump yy litres per minute. The viscosity difference then affects how much energy is needed to turn the pump at xxx rpm, and how quickly the oil will gravitate back to the sump.

 

[zeng]

Solarent, great job. Calling Shannow and other veterans .....

 

[ST2008]

I have a question. If 0W30 has better oil characteristics than 10W30 in cold temperature and they are the same at op temperatures, why the oil mfgs need to different grades ? What I means is why they don't just sell only 0W30 to everybody who need xW30?

 

[Jetronic]

It's more expensive to make a 0w30 than a 10w30

 

[BrocLuno]

Originally Posted By: Solarent

It is still too thick for normal operation. But it does not have as far to go as the 10W30, before it warms up and thins to the correct viscosity. Remember that most engine wear occurs at startup when the oil is too thick to lubricate properly. Most of the thick oil at startup actually goes through the bypass valve back to the engine oil sump and not into your engine oil galleys where it is spread to various engine components. This is especially true when you really step on that gas pedal. You really need more lubrication and you actually get less.

Sorry, I call B_S. 1.) You are alluding to flow as lubrication, and it is not. The presence or absence of oil IS lubrication. There are lots of small engines out there that do not have oil pumps at all, and they last years, if not decades. There are industrial and marine engines that have been running on gravity fed "drip" systems for millions of miles or tens of thousands of hours. In modern automotive engines, there are many parts that never see pumped oil, ever. But they do not wear out prematurely. Piston skirts, wrist pins, rings, cylinder walls, many cam/lifter systems (on the cam to lifter face), timing chains, distributor gears and oil pump drives are most likely not pressure fed. These systems rely on gravity feed from higher up, or sling oil off the spinning crankshaft. They run 100,000 miles at least w/o ever a drop of pressure fed oil. We have to get away from AE Haas's feed oil mislead ... Feed oil is for journal bearings mostly. Secondary feed oil is for rocker arms and such. 2.) The film strength of cold oil is quite high and it is everywhere inside an engine from the last shut-down. It is that residual oil film that is lubricating all surfaces at start-up. It has nothing to do with flow... There is no "less lubrication" going on with cold oil. In most cases there is more lubrication as the film is thicker and stronger. It takes work to spin parts in this thicker oil. But it is not a bad thing (except for parasitic drag and fuel economy). Now, it is true that the thicker oil does not sling nearly as well as warm thin oil. So there is a time of transition. But the engineers have done their homework and the residual oil film of cold oil is robust enough to protect most moving parts well beyond the time it takes for the engine to warm up and the oil to come to op temp. This may not be true for race motors that have to go 0-to WOT, so they get heated oil before staring. But it seems to work well enough for Fire Trucks and Ambulances all across the country including frozen Wisconsin winters ... Please walk away from AE Haas's flow arguments. They are not true. They are a major fallacy and mislead the public into wrong thinking ... I really like what you are doing. You are onto a much needed task. But this may be the only time we can get Helen and the Mods to allow changes, and we need speak truth if at all possible ...

 

[Solarent]

Thank's for your input. I agree that we need to edit/change/update the thinking in all aspects. This is why I took a stab at rewriting and posted it for comments/edits. For consistency I kept some of the original content - but if you feel we need to move away from it then I am totally fine with that. Please if you have the time draft some new paragraphs to replace the text so that it fits in the chapter and I will add it into my master copy. This way when/if the powers that be send me a message and ask for the updated text I have it ready to send to them.

 

[MolaKule]

Suggested modification to paragraph 9:

Originally Posted By: Solarent

Chapter Two – Oil Grades In chapter one we talked about how oil changes viscosity as the temperature increases and the challenge it is to keep close to the right operational viscosity regardless of the temperature. If the operating temperature is 212F and the recommended viscosity is 10cSt then OIL A which can be made to be 40 cSt at 104F(40C) is going to be better than OIL B that is 100cSt at 104F (40C). They will still be both too thick at start up and during the warm up period but OIL A will flow better and waste less energy. So when you buy an oil at the store you will see on it a grade which will read something like 5W30. This grade is based on the way the viscosity changes to temperature and references a standard chart called the SAE J300. I won’t bore you with the details of how the chart has changed over the years, but I will tell you that as engines and oils have developed, the system has been updated to reflect the current way oils are selected by engine manufacturers and oil makers. The system isn’t perfect but it is used worldwide, so understanding the basics of how it works and how it relates to your engine oil viscosity can help a great deal. The engine oil grade is divided into 2 parts: XW and YY to make XWYY (the X and YY are replaced with numbers). I like to think of this as a school grade that is made up of 2 parts – attendance and participation. In order to get the best grades in school you have to both show up and participate. If you only show up then you the grade won’t be the best; if you only show up some of the time your grade also won’t be the best, and either way you may not meet the requirements to pass the class. It is the same with engine oil grades. If you want the best grade for your engine, you need both parts of the grade together to meet the requirements of the engine builder’s specification. Instead of attendance and participation, for engine oils we have cold temperature performance and high temperature performance. Like I said we need both in order to do well. So this combination of the two parts XW and YY is called a “multi-grade”. Each part of the engine oil grade is based on different tests and have a different numbering system. For the first part (the cold temperature performance) it is based on the flow rate and pumpability at cold temperatures (below 32F or 0C). Each section of the rating scale is based on a range of numbers scored on standardized cold temperature tests. Since winter is cold and it is a good way to remember it, the W is used to indicate that this number is from the cold rating scale. From the lightest viscosity to the heaviest the scale is as follows: 0W, 5W, 10W, 15W, 20W, 25W. The second part (the high temperature performance) is based on the viscosity rating at 212F (100C) and how the oil responds to high temperatures and something called shear forces – or HTHS – this is an important number that will be talked about in a future chapter. Each section of the rating scale is based on standardized high temperature tests. From the lightest viscosity to the heaviest the scale is as follows 8, 12, 16, 20, 30, 40, 50, 60. So for an engine oil grade you have a combination of the first part (cold temperature performance) and the second part (high temperature performance) for example 5W30. When comparing oils you can say that 0W30, 5W30, 10W30 all have similar high temperature performance, with a range in cold temperature performance options. Similarly you could compare 0W16, 0W20, 0W30 and 0W40 as all having similar cold temperature performance, but a range in high temperature performance. Do you remember our 10 cSt example oil from Chapter 1? This fluid fits on the high temperature performance scale at 30 so it is an XW30 oil. If we were to compare a 0W30 and a 10W30 they all fit into the same category for the high temperature performance. Some people think that a 0W30 is way too thin and that it won’t protect your engine – We’ve heard people say that Porsche specifically prohibits a 0W30 engine oil for that reason. In reality, at operating temperature they would be the same! The difference is at 75F, your startup temperature in the morning: 10W30 Thickness at 75F: 100 cSt Thickness at 212 F: 10 cSt --- 0W30 Thickness at 75F: 40 cSt Thickness at 212 F: 10 cSt Now you can see that the difference between the desired thickness your engine requires ( = 10 ) is closest to the 0W-30 oil at startup. It is still too thick for normal operation. but the 0W30 does not have as far to go as the 10W30 before it warms up and thins to the correct viscosity. For a short period of time, some engine wear will occur upon startup until the oil wedges in parts clearances have been established. The oil film and additives that were deposited before shutdown will protect against excessive wear on startup. Most of the thick oil at startup actually goes through the bypass valve back to the engine oil sump until the oil warms up. On very cold winter mornings, it is good practice to drive slowly until the engine warms up in order reduce fuel consumption. So how does this happen? How can you have 2 oils with different grades both meet the same high temperature performance, yet one is much closer to the correct viscosity at startup? The answer is in how the oil is made.