Teach me about engine oil
Discussion
The very basics are-
1) Oil gets thinner as it heats up
2) Lower numbers and thinner, higher numbers are thicker.
The stats for the oils are because they are multigrade, the first number is what it is behaving like when cold, the second number is what it is behaving like when hot.
The ones with the biggest gaps between them are the most stable, and usually most expensive, somethine like a 10-60 starts off like a 10 weight oil, but when it heats up, it acts like a hot 60 weight, not a hot 10 weight, so it doesn't thin out as much.
Modern cars tend to be running thinner oils than years ago, stuff like 0-30's for most modern cars, and older engines from 20 years ago would often be on 10-40.
1) Oil gets thinner as it heats up
2) Lower numbers and thinner, higher numbers are thicker.
The stats for the oils are because they are multigrade, the first number is what it is behaving like when cold, the second number is what it is behaving like when hot.
The ones with the biggest gaps between them are the most stable, and usually most expensive, somethine like a 10-60 starts off like a 10 weight oil, but when it heats up, it acts like a hot 60 weight, not a hot 10 weight, so it doesn't thin out as much.
Modern cars tend to be running thinner oils than years ago, stuff like 0-30's for most modern cars, and older engines from 20 years ago would often be on 10-40.
Hi
This should help
- Engine Oil Viscosity -
Viscosity is the most misunderstood aspect of oil and yet it is the most important.
Viscosity is the force required to shear (break) the oil at a certain speed and temperature. Oils work because they have viscosity; the drag of a rotating part pulls oil from a low-pressure area into a high pressure area and “floats” the surfaces apart. This is called “hydrodynamic lubrication” and crank bearings depend on it.
Oil must be capable of flowing at low temperatures, so that it gets around the engine in a fraction of a second at start-up and must protect engine components at high temperatures without evaporating or carbonising and maintain adequate oil pressure.
The numbers on every can of oil indicate its performance characteristics when new but there are many misconceptions on what these numbers actually mean.
For multigrade oils you will see two numbers (for monograde oils only one). The first is followed by a “w” and is commonly 0, 5, 10, 15 or 20. The second number is always higher than the first and is commonly 20, 30, 40, 50 or 60. The first and second numbers ARE NOT related.
- The “w” number (0, 5, 10, 15 or 20) -
When multigrade oils first appeared, a low temperature test called “w” (meaning “winter” not weight) was introduced. Using a “Cold Crank Simulator, the test measures the oils ability to flow at low temperatures.
ALL oils are THICKER at low temperatures than at high temperatures but the lower the “w” number, the quicker the oil will flow at low temperatures.
- The second number (20, 30, 40, 50 or 60) -
This number is known as the SAE (Society of Automotive Engineers) number and is measured in “Centistokes” (cst) at 100oC.
Centistokes (cst) is the measure of a fluid's resistance to flow (viscosity). It is calculated in terms of the time required for a standard quantity of fluid at a Oil Viscosity certain temperature to flow through a standard orifice. The higher the value, the thicker the oil.
An oils cst at 100oC determines it’s SAE rating within the following parameters:
- SAE 20 = 5.6 to less than 9.3cst
- SAE 30 = 9.3 to less than 12.5cst
- SAE 40 = 12.5 to less than 16.3cst
- SAE 50 = 16.3 to less than 21.9cst
- SAE 60 = 21.9 to less than 26.0cst
A decent oil always falls in the middle of the specso an SAE 40 will be around 14cst.
ALL oils labelled 40 must fall within the SAE parameters at 100oC so everything from a monograde 40 to multigrade 0w-40, 5w-40, 10w-40, 15w-40 are the same thickness at 100degC.
- Summary -
- Cold start -
- A 5w-40 will flow better than a 10w-40
- A 10w-50 will flow better than a 15w-50
- A 5w-40 is the same as a 5w-30
- At operating temperatures -
- A 10w-50 is thicker than a 10w-40.
- A 15w-50 is thicker than a 5w-40
- A 0w-40 is the same as a 10w-40
Multigrades offer flexibility but manufacturers recommended viscosities should be observed unless modifications have been made that affect engine temperatures or the car is being used off road.
Cheers
Tim
This should help
- Engine Oil Viscosity -
Viscosity is the most misunderstood aspect of oil and yet it is the most important.
Viscosity is the force required to shear (break) the oil at a certain speed and temperature. Oils work because they have viscosity; the drag of a rotating part pulls oil from a low-pressure area into a high pressure area and “floats” the surfaces apart. This is called “hydrodynamic lubrication” and crank bearings depend on it.
Oil must be capable of flowing at low temperatures, so that it gets around the engine in a fraction of a second at start-up and must protect engine components at high temperatures without evaporating or carbonising and maintain adequate oil pressure.
The numbers on every can of oil indicate its performance characteristics when new but there are many misconceptions on what these numbers actually mean.
For multigrade oils you will see two numbers (for monograde oils only one). The first is followed by a “w” and is commonly 0, 5, 10, 15 or 20. The second number is always higher than the first and is commonly 20, 30, 40, 50 or 60. The first and second numbers ARE NOT related.
- The “w” number (0, 5, 10, 15 or 20) -
When multigrade oils first appeared, a low temperature test called “w” (meaning “winter” not weight) was introduced. Using a “Cold Crank Simulator, the test measures the oils ability to flow at low temperatures.
ALL oils are THICKER at low temperatures than at high temperatures but the lower the “w” number, the quicker the oil will flow at low temperatures.
- The second number (20, 30, 40, 50 or 60) -
This number is known as the SAE (Society of Automotive Engineers) number and is measured in “Centistokes” (cst) at 100oC.
Centistokes (cst) is the measure of a fluid's resistance to flow (viscosity). It is calculated in terms of the time required for a standard quantity of fluid at a Oil Viscosity certain temperature to flow through a standard orifice. The higher the value, the thicker the oil.
An oils cst at 100oC determines it’s SAE rating within the following parameters:
- SAE 20 = 5.6 to less than 9.3cst
- SAE 30 = 9.3 to less than 12.5cst
- SAE 40 = 12.5 to less than 16.3cst
- SAE 50 = 16.3 to less than 21.9cst
- SAE 60 = 21.9 to less than 26.0cst
A decent oil always falls in the middle of the specso an SAE 40 will be around 14cst.
ALL oils labelled 40 must fall within the SAE parameters at 100oC so everything from a monograde 40 to multigrade 0w-40, 5w-40, 10w-40, 15w-40 are the same thickness at 100degC.
- Summary -
- Cold start -
- A 5w-40 will flow better than a 10w-40
- A 10w-50 will flow better than a 15w-50
- A 5w-40 is the same as a 5w-30
- At operating temperatures -
- A 10w-50 is thicker than a 10w-40.
- A 15w-50 is thicker than a 5w-40
- A 0w-40 is the same as a 10w-40
Multigrades offer flexibility but manufacturers recommended viscosities should be observed unless modifications have been made that affect engine temperatures or the car is being used off road.
Cheers
Tim
Yep, you can mix oils, nothing bad happens.
Almost all current oils are suitable for everything, you don't tend to have diesel oils or petrol oils etc, they tend to be one standard that is good enough for everything.
The reason why manufacturers tell you to top up with the same type is because the more you top up, the more it slowly moves away from the original spec.
You'll end up with something inbetween 0-30 and 5-30, but it's not going to cause any harm.
The main thing that can catch people out is extended service intervals, and the oil the is designed for it, a lot of cars these days might have 20k oil changes, and longer life oil.
You wouldn't want to go the distance on a less capable oil, but certainly mixing them doesn't cause any weird chemical reactions, and I bet the handbook would mention a bunch of different oil grades for different ambient temps.
Almost all current oils are suitable for everything, you don't tend to have diesel oils or petrol oils etc, they tend to be one standard that is good enough for everything.
The reason why manufacturers tell you to top up with the same type is because the more you top up, the more it slowly moves away from the original spec.
You'll end up with something inbetween 0-30 and 5-30, but it's not going to cause any harm.
The main thing that can catch people out is extended service intervals, and the oil the is designed for it, a lot of cars these days might have 20k oil changes, and longer life oil.
You wouldn't want to go the distance on a less capable oil, but certainly mixing them doesn't cause any weird chemical reactions, and I bet the handbook would mention a bunch of different oil grades for different ambient temps.
opieoilman said:
Hi
This should help
- Cold start -
- A 5w-40 will flow better than a 10w-40
- A 10w-50 will flow better than a 15w-50
- A 5w-40 is the same as a 5w-30
- At operating temperatures -
- A 10w-50 is thicker than a 10w-40.
- A 15w-50 is thicker than a 5w-40
- A 0w-40 is the same as a 10w-40
Multigrades offer flexibility but manufacturers recommended viscosities should be observed unless modifications have been made that affect engine temperatures or the car is being used off road.
Cheers
Tim
Thanks that helps a lot, so i'm thinking on that basis that 0w40 would be the best, the car used about a litre of oil in 7000miles. so not burning any as near as it counts, would that be correct ?This should help
- Cold start -
- A 5w-40 will flow better than a 10w-40
- A 10w-50 will flow better than a 15w-50
- A 5w-40 is the same as a 5w-30
- At operating temperatures -
- A 10w-50 is thicker than a 10w-40.
- A 15w-50 is thicker than a 5w-40
- A 0w-40 is the same as a 10w-40
Multigrades offer flexibility but manufacturers recommended viscosities should be observed unless modifications have been made that affect engine temperatures or the car is being used off road.
Cheers
Tim
mcgandalf said:
My Volvo S60 D5 takes 0w30 oil (manufacturer's specification).
I have some 5w30 oil left over from my previous derv Vectra. Can I top up the Volvo 0w30 with the 5w30?
Hi I have some 5w30 oil left over from my previous derv Vectra. Can I top up the Volvo 0w30 with the 5w30?
What year is the Volvo? And what are the specs on the 5w-30? If that oil is an ACEA A5/B5, is should be safe for the Volvo.
Cheers
Tim
Viscosity ratings are determined by how "thick" the oil is. Each rating 20, 30, 50, whatever relates to a certain "thickness" of oil. The bigger the number, the "thicker". Old oils just had a single rating, because they behaved in a straight line, and thinned predictably as they got hot.
Many moons ago, when "multigrade" was new-fangled, they decided to give it two ratings, according to how it behaved at 0degC and at 100degC. If a multigrade was as "thick" as a 50-weight single grade oil hot, then the second number was 50. If it was as "thin" as a 20-weight oil cold, then the first number was 20, and you had a 20w50 (or 20-50, they mean the same).
Thinner, both hot and cold, and it'd be a 10-40. Or whatever. Don't forget that whilst "10" might be thinner than "40", cold "10" is still a lot thicker than hot "40". It just thins much less as it heats up than a straight 10 would.
Obviously, you don't want oil that's too thick when it's cold - it'd be like pumping treacle on a freezing morning. Equally, you don't want oil that's too thin hot, because it'll just dribble straight out of all those toasty-hot bearings and you'll have low oil pressure. Some modern engines are MUCH fussier than others, and than older engines used to be.
Then you've got the base - mineral, semi-synthetic or full-synthetic. Mineral is older-tech. Semi-synth and full-synth both start off as dead dinosaurs, but they get fiddled with by people in white coats, and end up being much more stable as temperatures rise, so they last longer. Ignore anybody who says "Oooh, you can't use synth in old engines, it'll fall out of all the seals" (or break up the muck holding the engine together or whatever). Obviously, putting a really thin oil into a worn old engine will give problems. Equally, any high-detergent oil will give problems if your engine's full of muddy goop. A full synth 10w40 will behave exactly like a semi-synth 10w40 or a mineral 10w40, except it'll be better at doing it, won't get knackered so easily or quickly, and won't turn into a burnt mess at the sight of a photo of a turbo.
Then you've got all the other additives and properties, "low ash" or whatever, and manufacturer approvals. Read your owner's handbook for what you're after there.
Many moons ago, when "multigrade" was new-fangled, they decided to give it two ratings, according to how it behaved at 0degC and at 100degC. If a multigrade was as "thick" as a 50-weight single grade oil hot, then the second number was 50. If it was as "thin" as a 20-weight oil cold, then the first number was 20, and you had a 20w50 (or 20-50, they mean the same).
Thinner, both hot and cold, and it'd be a 10-40. Or whatever. Don't forget that whilst "10" might be thinner than "40", cold "10" is still a lot thicker than hot "40". It just thins much less as it heats up than a straight 10 would.
Obviously, you don't want oil that's too thick when it's cold - it'd be like pumping treacle on a freezing morning. Equally, you don't want oil that's too thin hot, because it'll just dribble straight out of all those toasty-hot bearings and you'll have low oil pressure. Some modern engines are MUCH fussier than others, and than older engines used to be.
Then you've got the base - mineral, semi-synthetic or full-synthetic. Mineral is older-tech. Semi-synth and full-synth both start off as dead dinosaurs, but they get fiddled with by people in white coats, and end up being much more stable as temperatures rise, so they last longer. Ignore anybody who says "Oooh, you can't use synth in old engines, it'll fall out of all the seals" (or break up the muck holding the engine together or whatever). Obviously, putting a really thin oil into a worn old engine will give problems. Equally, any high-detergent oil will give problems if your engine's full of muddy goop. A full synth 10w40 will behave exactly like a semi-synth 10w40 or a mineral 10w40, except it'll be better at doing it, won't get knackered so easily or quickly, and won't turn into a burnt mess at the sight of a photo of a turbo.
Then you've got all the other additives and properties, "low ash" or whatever, and manufacturer approvals. Read your owner's handbook for what you're after there.
The manufacturers go for thinner oils these days as the tolerances are better and it is more economical to have a thin oil than a thick one as the moving parts encounter less resistance from a thinner grade than a thick one, multiply that thousands of times a minute, there is a measurable difference in economy between running a 0-30 or a 20-50.
You change it because the oil picks up soot from the combustion process, metal particles from the engine wearing, fuel sometimes slips past into the oil and water from the heating and cooling which introduces condensation, also it wears out at a molecular level and gets less effective, I sort of liken it to that time as a kid when you chewed your Bubble Gun too long and it went all weird, that's it not doing its job any more, the additives stop doing their job as well, this is partly why some engines that aren't serviced properly get all sludgy.
No reason for sludge in a modern, well serviced engine, they can effectively go on indefinitely when serviced correctly, treated sympathetically and given some regular stick !
My practice is to do all three cars, once a year, regardless of mileage with a quality Synthetic of an appropriate grade, new filter and new suump plug washer, basically there is very little else a modern car needs as a routine, plus last for ages now, no points, whack the air filter out and have a look and stick it back if it is ok, Coolant, brake fluid, cabin filter when they need doing, brake disks and pads when worn.
You change it because the oil picks up soot from the combustion process, metal particles from the engine wearing, fuel sometimes slips past into the oil and water from the heating and cooling which introduces condensation, also it wears out at a molecular level and gets less effective, I sort of liken it to that time as a kid when you chewed your Bubble Gun too long and it went all weird, that's it not doing its job any more, the additives stop doing their job as well, this is partly why some engines that aren't serviced properly get all sludgy.
No reason for sludge in a modern, well serviced engine, they can effectively go on indefinitely when serviced correctly, treated sympathetically and given some regular stick !
My practice is to do all three cars, once a year, regardless of mileage with a quality Synthetic of an appropriate grade, new filter and new suump plug washer, basically there is very little else a modern car needs as a routine, plus last for ages now, no points, whack the air filter out and have a look and stick it back if it is ok, Coolant, brake fluid, cabin filter when they need doing, brake disks and pads when worn.
Mr2Mike said:
The downside is that this is usually achieved by viscosity improver additives that tend to shear as the oil ages, resulting in a drop in viscosity.
For mineral yes but synthetic oils can achieve the multigrade property with much less VI improver and so are more 'shear stable'The handling of the dirt and worn metal particles is done by additives called dipsersants which hold the particles in the fluid and either deposit them in the filter or hold them in solution until the oil is drained. There are only a certain amount of dispersants in the oil and once they are all used up then any further particles are left to deposit themselves around the engine.
An oil turning 'black' is a good thing as it indicates all the dirt particles are held in solution in the oil and not deposited elsewhere.
There are also the same limitations for base additives which have the responsibility of cancelling out all the acids that are deposited in the oil as by-products of the combustion products.
Another example are 'surface active' additives which replace a film of additives on such items as bearings which is wiped off and replaced everytime the crank goes round.
In summary there are only limited levels of all these additives in oils and so when they run out then it's time to change the oil!
Use the recommended grade and change it at the defined intervals and you will be okay.
opieoilman said:
Hi
What year is the Volvo? And what are the specs on the 5w-30? If that oil is an ACEA A5/B5, is should be safe for the Volvo.
Cheers
Tim
It's an early 2005 S60 D5 with the Euro III engine (no DPF). What year is the Volvo? And what are the specs on the 5w-30? If that oil is an ACEA A5/B5, is should be safe for the Volvo.
Cheers
Tim
The oil is ACEA C3-10. Millers EE Longlife Nanodrive.
You sold it to me, incidentally.
This is information from a chemist friend who works for an oil testing company.
Background
There are four engine oil additive companies in the world; Afton, Infineum, Lubrizol and Oronite. They supply around 90 % of the additives used in engine oil in the entire world and 100 %of the additive packages used in oils with official claims. The other oils simply carry a manufacturing quality claim, in other words state that the oil is made to correct manufacturing specification, but does not have any tested performance in an engine.
The four additive companies not only supply individual additives, but design and test oils containing specific packages to meet engine oil claims. These additive packages and specific oil mixes are then sold to oil marketers where it is sold under commonly [and less commonly] known oil brands.
To state this more explicitly, the additive companies are responsible for taking an oil brief to a final oil that may be sold under a brand name, sometimes the larger oil marketers run their own programs internally, however the additive companies must still manufacture and supply the additives in order for this to happen.
I work for one of the four additive companies, and am writing this purely to provide factually accurate and unbiased information on engine oils; due to the number of oil marketers we supply, it is impossible to try to push or sell a single product through this article.
Oil technology
There are different grades of base stock that are used in an engine oil, they can be broken down as follows;
Group 1; oil sourced from crude oil with fairly low processing, high in sulfur and aromatic content. Viscosity changes greatly with temperature
Group 2; as group 1 with slightly more refining, resulting in less sulfur and less aromatic content.
Group 3. Highly processed crude oil, resulting in less temperature change in viscosity with temperature and low sulfur.
Group 4. Oil assembled synthetically, resulting in very controlled structure giving very low sulfur, very good viscosity control and low aromatic content
Group 5; everything else, typically very expensive and with specialist applications.
Small changes in viscosity with temperature means that the performance of the oil becomes very predictable at a range of temperatures, allowing it to maintain good lubrication and protection of engine parts.
Sulfur may form acidic species in the oil, which in turn reacts with and corrodes metal parts in the engine.
Aromatic content may be chemically attacked leading to viscosity growth of the oil and poor lubrication during the life of the oil, they could also lead to low temperature pumpability problems by forming gel structures, causing oil starvation.
There is disagreement as to whether group 3 oils are synthetic, they have a great degree of processing applied to them in comparison to group 1 and 2, in turn producing a much more controlled and higher performing base stock, however are sourced from crude oil and therefore not truly synthetic. Some countries allow the oil to be labeled as synthetic, others semi-synthetic, some not at all. As you will find out, it doesn’t make much of a difference.
Additive technology.
The base stock alone cannot adequately protect an engine, this can be seen in this report here:http://www.ilma.org/...qualityoils.pdf which compares an API SA oil [minimal performance claims, just base stock] with SL [a much later claims set requiring more in the oil than just base stock]
In order to add performance to the oil, the following chemicals are added:
Detergents
Added to remove varnish and deposits produced during the combustion process, most deposits and lacquer form in the cylinder and on the piston, at the hottest points as it’s typically formed from partially combusted fuel and engine oil.
Detergents also neutralise acids produced in the engine by the combustion process [fuels contain nitrogen and sulfur which form nitric and sulfuric acid in the engine], which prevents acidic corrosion of parts in the engine.
Anti-wear agents
Anti-wear agents decompose and form ‘sacrificial surfaces’ between rubbing contacts to protect the metal from wear. This is typically through the use of ZnDDP or ZDDP, the first commercial additive which demonstrated a clear benefit in the engine, and in use for around 80 years.
Dispersants
Incompletely combusted fuel, and insoluble particles will agglomerate and form highly structured networks in oil which causes viscosity to increase. Dispersants suspend these species in the oil and separate them, preventing viscosity increase.
Anti-oxidants
High temperature causes chemicals to split and turn into reactive species, metal in the engine acts as catalysts and increases the rate this happens. The reactive species attack anything available; oil, fuel and additives which causes degradation of the oil and viscosity increase. Anti-oxidants trap these attacking species to protect the oil
Viscosity modifiers
While high quality base stocks maintain some viscosity control with increasing temperature, it’s not sufficient to avoid very viscous oil at cold and very thin oil at high temperature. This leads to oil starvation and inadequate protection of the surfaces respectively. Viscosity modifiers collapse at low temperature but unfurl at high temperature, interacting with the base stock and creating an ordered structure in the oil, which increases viscosity. This allows an oil to be used all year around and provide engine protection over a wide range of temperatures
Pour point depressors
Poor quality base stocks or used oils form large gel structures at low temperature, when the engine is started the pump sucks up oil from the sump, if there are gel structures the oil will not flow and will cause oil starvation, pour point depressors break up the gel structures to ensure the oil flows.
Friction modifiers
Designed to reduce the energy losses created between rubbing metal surfaces, they are used more in America and Japan as the energy, and thus fuel saving is minor and therefore driven by legislation rather than a consumer saving.
Anti-foam
Prevents foaming in oil filters which can cause oil blockages.
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Why less is more
The problem with all these additives is they interact when they are combined, each group of additives have a wide range of chemicals that act at different temperatures, under different pressures or work on different part of chemical cycles. There are countless implications to consider when combining the additives, some examples:
More ZDDP should mean better anti-wear, however high ZDDP introduces more phosphorus, which can be burnt off and enter the catalytic converter, phosphorus poisons catalytic converters by blocking binding sites, resulting in a very expensive service by MOT time.
More dispersant means better viscosity control, but reacts with seals causing swelling, cracking and energy loss. Eventually this leads to an engine rebuild to replace all the failed parts.
More detergent means better deposit control, but the detergent is surface active and competes on metal surfaces with ZDDP, too much detergent and wear protection gets compromised.
What to look out for
All the attributes such as wear protection, viscosity control and deposit control are tested for, and indicated by the specification on the back of an oil. Oil sold in Europe will carry ACEA specification; the concept being with ACEA specification is a minimum standard for all oil, where any additional claims by engine manufacturers are added on top to boost performance. The ACEA claims are broken down as follows;
A/B mean suitable for petrol and diesel engines, C is suitable for engines with after treatment devices [such as diesel particulate filters and 3 way catalytic converters]. There is a number that follows the letter, where:
A1/B1 = good fuel economy with average engine performance
A3/B3 = normal fuel economy with average engine performance
A3/B4 = normal fuel economy with good engine performance
A5/B5 = good fuel economy with good engine performance
The date provided with the ACEA recommendations made for your car will be related to the date of manufacture, if you go for a newer year [eg. You are recommended ACEA ’04 and go for ACEA’10], you will have a better quality oil as the requirements improve each year.
A1/B1 and A5/B5 have reduced detergent inorder to allow for additional engine compatability, avoid them if your manual recommends A3/B3 or A3/B4. Always go for A3/B4 or A5/B5 compared to A3/B3 or A1/B1 respectively if given the choice, they offer tighter cam, tappet and piston wear limits than the former.
Proof
The oils with ACEA claims have undergone multiple engine tests designed to test the extreme point of operation of the engine, the current ACEA specification use the following tests:
TU5 high temperature deposit, ring sticking and oil thickening test [72 hour test]
Sequence VG low temperature sludge test[216 hour test]
TU3 Valve train wear test [100 hour test]
M271 sludge test
M111 fuel economy test
DV4 dispersancy test
OM646LA cam and tappet wear test [268hours]
VW TDI diesel piston cleanliness test [58hours]
Engine manufacturers have additional tests, some use bench tests to look at turbo charger deposits, others have much more stringent wear tests; the VW 504/507 specification requires a 650 hour weartest.
All these tests operate on the edge of what is considered normal operation, and typically much harsher than normal conditions. Any oil carrying the correct ACEA claims will be able to provide more than adequate protection for an engine, for additional protection I would recommend looking for an oil with a larger claim set, specifically one with VW claims as they typically have harsher limits.
There is no need to look for specialist engine oil; if it doesn’t have ACEA claims there’s no protection or proof that it is capable of protecting your engine. They are strict tests, and with a typical cost of around £70,000 a test, really do show confidence in the product.
Background
There are four engine oil additive companies in the world; Afton, Infineum, Lubrizol and Oronite. They supply around 90 % of the additives used in engine oil in the entire world and 100 %of the additive packages used in oils with official claims. The other oils simply carry a manufacturing quality claim, in other words state that the oil is made to correct manufacturing specification, but does not have any tested performance in an engine.
The four additive companies not only supply individual additives, but design and test oils containing specific packages to meet engine oil claims. These additive packages and specific oil mixes are then sold to oil marketers where it is sold under commonly [and less commonly] known oil brands.
To state this more explicitly, the additive companies are responsible for taking an oil brief to a final oil that may be sold under a brand name, sometimes the larger oil marketers run their own programs internally, however the additive companies must still manufacture and supply the additives in order for this to happen.
I work for one of the four additive companies, and am writing this purely to provide factually accurate and unbiased information on engine oils; due to the number of oil marketers we supply, it is impossible to try to push or sell a single product through this article.
Oil technology
There are different grades of base stock that are used in an engine oil, they can be broken down as follows;
Group 1; oil sourced from crude oil with fairly low processing, high in sulfur and aromatic content. Viscosity changes greatly with temperature
Group 2; as group 1 with slightly more refining, resulting in less sulfur and less aromatic content.
Group 3. Highly processed crude oil, resulting in less temperature change in viscosity with temperature and low sulfur.
Group 4. Oil assembled synthetically, resulting in very controlled structure giving very low sulfur, very good viscosity control and low aromatic content
Group 5; everything else, typically very expensive and with specialist applications.
Small changes in viscosity with temperature means that the performance of the oil becomes very predictable at a range of temperatures, allowing it to maintain good lubrication and protection of engine parts.
Sulfur may form acidic species in the oil, which in turn reacts with and corrodes metal parts in the engine.
Aromatic content may be chemically attacked leading to viscosity growth of the oil and poor lubrication during the life of the oil, they could also lead to low temperature pumpability problems by forming gel structures, causing oil starvation.
There is disagreement as to whether group 3 oils are synthetic, they have a great degree of processing applied to them in comparison to group 1 and 2, in turn producing a much more controlled and higher performing base stock, however are sourced from crude oil and therefore not truly synthetic. Some countries allow the oil to be labeled as synthetic, others semi-synthetic, some not at all. As you will find out, it doesn’t make much of a difference.
Additive technology.
The base stock alone cannot adequately protect an engine, this can be seen in this report here:http://www.ilma.org/...qualityoils.pdf which compares an API SA oil [minimal performance claims, just base stock] with SL [a much later claims set requiring more in the oil than just base stock]
In order to add performance to the oil, the following chemicals are added:
Detergents
Added to remove varnish and deposits produced during the combustion process, most deposits and lacquer form in the cylinder and on the piston, at the hottest points as it’s typically formed from partially combusted fuel and engine oil.
Detergents also neutralise acids produced in the engine by the combustion process [fuels contain nitrogen and sulfur which form nitric and sulfuric acid in the engine], which prevents acidic corrosion of parts in the engine.
Anti-wear agents
Anti-wear agents decompose and form ‘sacrificial surfaces’ between rubbing contacts to protect the metal from wear. This is typically through the use of ZnDDP or ZDDP, the first commercial additive which demonstrated a clear benefit in the engine, and in use for around 80 years.
Dispersants
Incompletely combusted fuel, and insoluble particles will agglomerate and form highly structured networks in oil which causes viscosity to increase. Dispersants suspend these species in the oil and separate them, preventing viscosity increase.
Anti-oxidants
High temperature causes chemicals to split and turn into reactive species, metal in the engine acts as catalysts and increases the rate this happens. The reactive species attack anything available; oil, fuel and additives which causes degradation of the oil and viscosity increase. Anti-oxidants trap these attacking species to protect the oil
Viscosity modifiers
While high quality base stocks maintain some viscosity control with increasing temperature, it’s not sufficient to avoid very viscous oil at cold and very thin oil at high temperature. This leads to oil starvation and inadequate protection of the surfaces respectively. Viscosity modifiers collapse at low temperature but unfurl at high temperature, interacting with the base stock and creating an ordered structure in the oil, which increases viscosity. This allows an oil to be used all year around and provide engine protection over a wide range of temperatures
Pour point depressors
Poor quality base stocks or used oils form large gel structures at low temperature, when the engine is started the pump sucks up oil from the sump, if there are gel structures the oil will not flow and will cause oil starvation, pour point depressors break up the gel structures to ensure the oil flows.
Friction modifiers
Designed to reduce the energy losses created between rubbing metal surfaces, they are used more in America and Japan as the energy, and thus fuel saving is minor and therefore driven by legislation rather than a consumer saving.
Anti-foam
Prevents foaming in oil filters which can cause oil blockages.
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Why less is more
The problem with all these additives is they interact when they are combined, each group of additives have a wide range of chemicals that act at different temperatures, under different pressures or work on different part of chemical cycles. There are countless implications to consider when combining the additives, some examples:
More ZDDP should mean better anti-wear, however high ZDDP introduces more phosphorus, which can be burnt off and enter the catalytic converter, phosphorus poisons catalytic converters by blocking binding sites, resulting in a very expensive service by MOT time.
More dispersant means better viscosity control, but reacts with seals causing swelling, cracking and energy loss. Eventually this leads to an engine rebuild to replace all the failed parts.
More detergent means better deposit control, but the detergent is surface active and competes on metal surfaces with ZDDP, too much detergent and wear protection gets compromised.
What to look out for
All the attributes such as wear protection, viscosity control and deposit control are tested for, and indicated by the specification on the back of an oil. Oil sold in Europe will carry ACEA specification; the concept being with ACEA specification is a minimum standard for all oil, where any additional claims by engine manufacturers are added on top to boost performance. The ACEA claims are broken down as follows;
A/B mean suitable for petrol and diesel engines, C is suitable for engines with after treatment devices [such as diesel particulate filters and 3 way catalytic converters]. There is a number that follows the letter, where:
A1/B1 = good fuel economy with average engine performance
A3/B3 = normal fuel economy with average engine performance
A3/B4 = normal fuel economy with good engine performance
A5/B5 = good fuel economy with good engine performance
The date provided with the ACEA recommendations made for your car will be related to the date of manufacture, if you go for a newer year [eg. You are recommended ACEA ’04 and go for ACEA’10], you will have a better quality oil as the requirements improve each year.
A1/B1 and A5/B5 have reduced detergent inorder to allow for additional engine compatability, avoid them if your manual recommends A3/B3 or A3/B4. Always go for A3/B4 or A5/B5 compared to A3/B3 or A1/B1 respectively if given the choice, they offer tighter cam, tappet and piston wear limits than the former.
Proof
The oils with ACEA claims have undergone multiple engine tests designed to test the extreme point of operation of the engine, the current ACEA specification use the following tests:
TU5 high temperature deposit, ring sticking and oil thickening test [72 hour test]
Sequence VG low temperature sludge test[216 hour test]
TU3 Valve train wear test [100 hour test]
M271 sludge test
M111 fuel economy test
DV4 dispersancy test
OM646LA cam and tappet wear test [268hours]
VW TDI diesel piston cleanliness test [58hours]
Engine manufacturers have additional tests, some use bench tests to look at turbo charger deposits, others have much more stringent wear tests; the VW 504/507 specification requires a 650 hour weartest.
All these tests operate on the edge of what is considered normal operation, and typically much harsher than normal conditions. Any oil carrying the correct ACEA claims will be able to provide more than adequate protection for an engine, for additional protection I would recommend looking for an oil with a larger claim set, specifically one with VW claims as they typically have harsher limits.
There is no need to look for specialist engine oil; if it doesn’t have ACEA claims there’s no protection or proof that it is capable of protecting your engine. They are strict tests, and with a typical cost of around £70,000 a test, really do show confidence in the product.
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