This might help some of you out, it's from a chap who is a oil chemist. Take from it what you will.
BackgroundThere 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 technologyThere 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:
DetergentsAdded 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 agentsAnti-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 modifiersWhile 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 depressorsPoor 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 modifiersDesigned 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.
Version:1.0StartHTML:0000000178EndHTML:0000004102StartFragment:0000002381EndFragment:0000004066SourceURL:file://localhost/Users/tomfeatherstone/Desktop/Background.doc
Why less is moreThe 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 forAll 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.
ProofThe 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.
ACEA ClaimsGoing back to the types of ACEA claims an oil carries, they can be broken down into two groups with two tiers;
Increased fuel economy
A1/B1 = average engine protection
A5/B5 = increased engine protection
Standard fuel economy
A3/B3 = average engine protection
A3/B4 = increased engine protection
Car fuel economy is dictated by legislation, there is only around a 1 % boost in fuel saving so the governing bodies have to legislate rather than sell the concept to the end user. Engine performance is almost always compromised to reach better fuel economy - not to the point that the engine oil is bad, simply that it won't perform as well as a cheaper, non-fuel saving oil.
As far specific applications go, there are a few key factors;
Rate of usageInfrequent use leads to rust forming inside the engine; car manufacturers have the same problem between manufacturing and selling a car - they have specific corrosion tests that they include in the factory fill oil. Unfortunately it is very hard to source a factory fill oil, following the recommended service fill oil may provide you with the same oil type.
Type of usageTrack use compared to road use introduces very different stresses, engines used in track cars typically see hotter pistons and require greater oxidation control. Beware of 'true' race oils as the engines are expected to be rebuilt regularly so may not protect soft metal in bearings or may be too low in viscosity [lower viscosity = better energy transfer = more performance, however more stress]. Always ensure the oil has ACEA specifications too. I would suggest the best approach would be to run a normal oil and halve the change interval.
NA vs. Turbo vs. Supercharged
Honestly, there's not much difference here. Some oils are specified as turbo or supercharger compatible, this is usually for one of two reasons; marketing, or it's an oil sourced from America.
The key difference for the oil in forced induction engines is the charger bearings; they get to very high temperatures [particularly turbo chargers] and the flow of oil stops with the engine turning off, this leaves stationary oil to cook and form deposits on the bearings. With time these deposits cause the blade axis to wobble and eventually leads to the blades hitting the casing, causing catastrophic failure.
European engine oil has had to cope with turbocharged diesel engines for decades, American oil doesn't because diesel use is not widespread. This means that all ACEA oils assume the oil may have to cope with forced induction.
If you are using an uprated charger, the best oil you can get is one with VW 504/507 claims; this is one of the harshest tests for an oil and involves a 650 hour engine test, it also involves a series of four 'black box' engine tests where VW test out the next generation of engines, these inevitably include an iteration of their dual supercharged, turbocharged small capacity engine which is a severe test for charger deposit control.
The Cal-look Lounge
Author
